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Bulletin  No.  44.  216 

U.  S.  DEPARTMENT  OF  AGRICULTURE. 

OFFICE   OF    EXPERIMENT    STATIONS. 


REPORT 


OF 


PRELIMINARY  INVESTIGATIONS 


ON  THE 


METABOLISM  OF  NITROGEN  AND  CARBON 
IN  THE  HUMAN  ORGANISM, 


WITH 


A  RESPIRATION  CALORIMETER  OF  SPECIAL  CONSTRUCTION. 


BY 


W.  0.  ATWATER,  Ph.  D.,  C.  D.  WOODS,  B.  S.,  and  P.  6.  BENEDICT,  Ph.  D. 

• 


WASHINGTON: 

GOVERNMENT    PRINTING    OFFICE. 
18U7. 


Bulletin  No.  44. 

U.  S.  DEPARTMENT  OF  AGRICULTURE. 

OFFICE    OF    EXPERIMENT    STATIONS. 


REPORT 


OF 


PRELIMINARY  INVESTIGATIONS 


ON  THE 


METABOLISM  OF  NITROGEN  AND  CARBON 
IN  THE  HUMAN  ORGANISM, 


WITH 


A  RESPIRATION  CALORIMETER  (IE  SPECIAL  CONSTRUCTION. 


W.  0.  ATWATER,  Ph.  D.,  C.  D.  WOODS,  B.  S.,  and  F.  G.  BENEDICT,  Ph.  D. 


WASHINGTON: 

GOVEKXMKNT    I'l'tf.VTINt;    OFFICE. 
I.SD7. 


LETTER    iW    TRANSMITTAL. 


U.  S.  Department  of  Agrkjultitrb, 

Office  of  Experiment  Stations, 

Washinytoii,  I).  C,  'June  W,  i.s'.V7'. 

Sir  :  I  have  the  honor  to  trausniit  herewith  a  report  of  iuve.sti.ua- 
tioii.s  ou  tlie  inetabolism  of  man,  in  the  conduct  of  which  a  respiration 
calorimeter  of  special  construction  was  used.  The  experiments  with 
nii'ii  herein  reported  were  made  in  the  winter  of  1895-90,  at  Middle- 
town,  Conn.,  under  the  immediate  supervision  of  Prof.  W.  O.  Atwater, 
special  agent  in  charge  of  nutrition  investigations.  These  experi- 
ments were,  liowever,  only  made  i)ossible  by  previous  researches  with 
si)ecial  reference  to  the  development  of  the  apparatus  and  methods  of 
intpiiry. 

This  work  was  begun  in  18915  under  the  direction  of  Professor 
Atwater  in  connection  with  his  duties  as  professor  of  chemistry  in 
Wesleyan  University  and  director  of  the  Storrs  Agricultural  Experi- 
ment Station.  Prof.  E.  1>.  liosa,  of  Wesleyan  University,  was  asso- 
ciated with  the  incpiiry,  on  the  physical  side,  from  the  outset.  When 
investigations  on  the  food  and  nutrition  of  man  were  undertaken  by 
this  Department  in  the  fall  of  1894,  exi)eriments  with  the  respiration 
calorimeter  were  made  a  part  of  the  general  plan  of  work,  and  it  was 
decided  to  extend  financial  aid  to  these  special  investigations,  which 
were  already  well  advanced  and  gave  i)romise  of  successful  issue. 
Since  that  time  these  iinjuiries  have  been  conducted  by  the  cooperation 
of  this  Department,  the  Storrs  Experiment  Station,  and  Wesleyan 
University.  In  this  way,  by  the  expenditure  of  conjparatively  small 
sums  for  the  [)romotion  of  this  particular  investigation,  the  De[)artment 
lias  been  able  to  secure  for  publi(;ation  the  results  of  a  large  amount  of 
original  research  in  a  line  of  vital  importance  in  connection  with  the 
establishment  of  a  scicntilic  basis  for  the  nutrition  of  num.  The  work 
on  the  res])iratiori  calorimeter  was  far  enough  advanced  by  the  winter 
of  lS9.">-90  to  justify  its  use  in  experiments  with  men.  After  several 
preliminary  trials,  the  data  from  which  were  too  incomplete  to  warrant 
publication,  but  which  were  of  great  service  iti  i)erfecting  arrangements 
for  the  succeeding  trials,  the  four  experiments  reported  in  this  bulletin 
were  made. 

NN'hile  all  tlu;  details  of  these  experiments  are  not  yet  ])erfe(;tly  satis- 
factory and  there  is  still  room  for  further  injprovement  of  the  apparatus 
to  be  used  in  sue!)  intricate  investigations,  they  nevertheless  mark  a 


decided  advance  over  work  of  similar  character  hitherto  published 
and  give  great  encouragement  to  continued  researches  in  this  line. 

The  greatest  success  thus  far  has  been  in  the  measurement  of  the 
metabolism  of  nitrogen  and  carbon,  and  the  present  report  is  devoted 
chiefly  to  the  chemical  side  of  the  investigation,  which  includes  these 
measnremeuts.  When  these  experiments  were  made  the  work  on  the 
physical  side,  although  carried  on  with  great  skill  and  with  highly 
interesting  results,  had  not  given  data  sufficiently  accurate  in  all  their 
details  to  make  its  publication  seem  advisable.  The  investigations  are 
proceeding,  changes  in  tbe  apparatus  have  already  resulted  in  very 
satisfactory  physical  measurements,  and  it  is  hoped  befoi^e  long  to  pub- 
lish more  complete  data  on  both  the  physical  and  chemical  sides  of  the 
work. 

The  general  management  of  these  investigations  has  devolved  upon 
Professor  Atwater.  In  devising  and  elaborating  the  apparatus  and  in 
the  carrying  out  of  that  part  of  the  investigation  which  relates  to  the 
measurement  of  the  heat  given  off  from  the  body  and  the  mechanical 
work  done.  Dr.  E.  B.  liosa,  professor  of  i)hysics  of  Wesleyan  Univer- 
sity, has  rendered  invaluable  service.  It  is  expected  that  in  later 
reports  Professor  Kosa  will  appear  as  joint  author  in  the  discussion  of 
the  investigations  from  the  physical  standpoint.  On  the  chemical  side, 
Dr.  Atwater  has  had  the  assistance  of  Prof.  O.  D.  Woods  and  Dr. 
F.  G.  Benedict,  joint  authors  of  this  report.  The  skill  and  ingenuity 
of  the  university  mechanician,  Mr.  O.  S.  Blakeslee,  have  also  contrib- 
uted in  no  small  degree  to  the  practical  embodiment  and  successful 
working  of  the  various  devices  adopted  for  the  perfecting  of  the  aj)pa- 
ratus.  Other  workers  whose  services  deserve  special  recognition  are 
A.  W.  Smith,  O.  F.  Tower,  A.  P.  Bryant,  and  H.  M.  Burr. 

This  report  is  respectfully  submitted,  with  the  recommendation  that 
it  be  published  as  Bulletin  No.  44  of  this  Oftice. 
Eespectfully, 

A.  C.  True, 

Director. 

Hon.  James  Wilson, 

JSecretary  of  Agriculture. 


CONTENTS. 


Page. 

iNTUt  )nrcTiox 7 

( loueral  statement 7 

The  experiments  reported  in  tliis  bulletin 10 

ArPAUATUS 11 

The  resi)iiatiou  ehaniher 12 

Appliances  for  ventilation  and  for  the  measurement  and  analysis  of  the 

ventilatiui,'  current  of  air 16 

Air  pump 18 

Tension  equalizer !!• 

Meter  for  measuring  air 19 

Aspirators  for  sampling  air 20 

Apparatus  for  determining  earbon  dioxid  and  water  in  sniuples  of  air.  21 

Methods  ov  samplixh  ani>  analysis 22 

Analysis  of  food,  feces,  and  urine 22 

Preparation  and  sampling  of  food 22 

Water.. 24 

Fat — Ether  extract 25 

Ash 25 

Nitrogen — Protein 25 

(Jarbon  and  hydrogen 26 

Heats  of  combustion — Fuel  values 26 

Collecting,  jjreserving,  and  sampling  of  feces  and  urine 26 

Analysis  of  respiratory  pioducts 27 

Carbon  dioxid 27 

Water 20 

Volatile  organn-  compounds 31 

The  experiments 31 

The  diet 32 

Daily  routine 31 

Computation  of  icsults 35 

Nitrogen  l)a]an<e 35 

Carbon  lialance 37 

Cain  ami  loss  oi'  jiroteiu  aTid  fat 3S 

Energy 39 

l{espiration  experiment  No.  1  (Digestion  experiment  No.  11) 40 

Respiration  <-xperiment  No.  2  (Digestion  experiment  No.  12) 45 

Respiration  experiment  No.  3  (Digestion  expeiiment  No.  13) 4S 

Respiration  experiment  No.  4  (Digestion  expf^rimeut  No.  14) 51 

1  MscuHsion  oC rr-snlts 56 

V^cntilatioii  and  jiroduction  of  earbon  dioxid 5(5 

Nutrients  :ind  (nel  \  iilues 5.S 

Conclusions 63 


ILLUSTRATIONS. 


Pajre 
Fig.  1.  Eespiration  calorimeter 11 

2.  Plau  of  rt'spiration  calorimeter  room , 13 

3.  Elevation  of  respiration  ealorimeter  room 15 

4.  Outline  sketch  of  respiration  apparatus 17 

6 


METABOLISM  OF  NITROGEN  AND  CARBON  IN  THE  HUMAN 

ORGANISM. 


INTRODUCTION. 

Ill  order  to  ascertain  the  vvuy.s  in  which  food  is  used  in  tlie  body  and 
the  kinds  and  amounts  which  are  best  suited  to  people  of  different 
classes  and  under  ditti^rent  conditions  it  is  necessary  to  devise  accurate 
methods  of  determining^  the  total  income  and  out^o  of  material  and 
energy  in  the  organism.  The  importance  of  such  a  study  of  the  funda- 
mental xmnciples  of  nutrition  luis  been  recognized  for  nuuiy  years,  and 
studies  of  one  or  more  of  the  factors  of  the  income  and  outgo  (espe- 
cially of  nitrogen)  have  received  much  attention  by  investigators  in 
this  field  of  science.  In  experiments  of  this  nature  it  is  customary  to 
express  the  results  as  a  balance,  in  which  the  outgo  is  subtracted  from 
the  income,  thus  showing  the  gain  or  loss. 

GENERAL    STATEMENT. 

So  far  as  the  balance  of  material  is  concerned,  the  income  consists  of 
food,  drink,  and  oxygen  of  inhaled  air;  and  the  outgo  consists  of  feces, 
urine,  and  the  products  of  resi)iration  and  perspiration.  A  complete 
ex]»eriment  on  the  metabolism  of  material  would  involve  determiimtions 
of  the  total  amount  of  oxygen  consumed,  the  amounts  and  tlie  elemen- 
tary and  ])roximate  composition  of  food,  feces,  urine,  and  products  of 
respiration  and  perspiration  (including  marsh  gas  from  the  intestines, 
and  similar  products).  For  the  balance  of  energy,  the  income  would 
include  the  potential  energy  of  the  food  and  drink;  the  outgo  wfmld 
inchide  the  potential  energy  of  feces  and  urine,  jtroducts  of  resi)iration 
and  |)erspiration,  and  the  kinetic  energy  given  off  in  heat  from  the 
body  ami  the  medianical  <mergy  of  the  external  muscular  work  per- 
formed. It  is  possible  that  other  less  familiar  forms  of  energy  may  be 
concerned,  but  these  are  all  which  are  at  present  known  and  which 
may  be  measured.  Due  account  must  of  course  be  taken  of  the  tem- 
j)erature  and  specific  heats  of  food,  drink,  ami  excretory  ])roducts,  aiul 
the  h(;at  used  or  evolved  in  the  condensation  of  the  watei- of  exhalation. 

A  complete  metabolism  e\perinu*nt  would  involve,  therefore,  the 
determination  of  the  following  factors  of  income  and  outgo  of  matter 
and  energy: 

Factor X  of  income. 

Matt<!i':  I'ood,  drink,  ox.vf^eii  of  iiir. 

KleriH-.rifH  of  food,  driiift,  and  air:  N,  C.  11,  O,  S,  P,  CI,  K,  Na,  Mg,  Ca,  Fe. 
(.*om|;oundH  of  food  and  drink:   Water,  jtrotcin  fompoinids,  fatu,  carbohy- 
diat'-H,  anri  mineral  niatterH. 
Energy:  Potential  energy  of  (organic)  corripoiinds  of  fi)o<l  ami  (iiiiil<. 

7 


Factorfs  of  outgo. 

Matter:  Feces,  urine,  products  of  respiration  and  perspiration. 

Elements  of  above:  N,  C,  H,  O,  S,  P,  CI,  K,  Na,  Mg,  Ca,  Fe. 
Compounds:  Water  of  urine  and  feces;  carbohydrates  and  mineral  matter 
of  feces;  organic  and  mineral  compounds  of  urine;  COj,  H.2O,  and  organic 
compounds,  etc.,  of  products  of  respiration  ard  perspiration. 
Energy:  Potential  energy  of  (organic)  compounds  of  feces,  urine,  and  products  of 
respiration  and  perspiration. 
Kinetic  energy  given  off  from  the  body,  as  beat,  external  muscular  work, 
and  possibly  in  other  forms. 

Tbe  above  statement  is,  liowever,  incomplete  in  tliat  it  does  not 
take  into  account  the  material  which  the  body  gains  or  loses  during 
the  experiment  and  the  corresponding  energy  stored  or  transformed. 
This  material  consists  mainly  of  water,  protein  compounds,  and  fats, 
with  smaller  amounts  of  carbohydrates,  mineral  matters,  and  other 
compounds. 

The  above  factors  represent  the  gross  income  and  outgo.  The  net 
income  would  include  only  the  material  wiiicli  the  body  actually  util- 
izes from  food,  drink,  and  air;  that  is,  it  represents  the  income  of  nutri- 
ents, water,  and  energy  consumed  minus  the  unassimilated  jiortion 
excreted  iu  the  feces,  taking  into  account  also  the  incomjdetely  oxi- 
dized matter  iu  the  urine,  Tlie  net  income  of  material  is  that  which  is 
taken  into  tlie  circulation,  builds  and  repairs  tissue,  and  yields  energy. 
The  net  income  of  energy  is  the  jiotential  energy  of  this  ]naterial  plus 
the  energy  received  with  the  food  and  drink  in  the  form  of  heat. 

The  gross  outgo  includes  the  total  material  of  the  excretory  products, 
and  the  sum  of  their  potential  energy  and  the  kinetic  energy  given  off 
from  the  body.  The  net  outgo  is  made  up  of  the  excretions  of  the  kid- 
neys, lungs,  and  skin,  and  the  sum  of  their  potential  energy  and  the 
kinetic  energy  given  off  from  the  body.  The  material  and  the  poten- 
tial energy  of  the  feces  are  not  utilized,  but  simply  rejected.' 

Metabolism  experiments  may  include  the  measurement  of  the  income 
and  outgo  of  one  or  more  of  the  above  factors.  Wlien  the  balance  of 
nitrogen,  with  or  without  mineral  matter,  is  determined,  the  only  fac- 
tors of  outgo  which  enter  into  account  are  the  urine  (sometimes  includ- 
ing the  perspiration)  and  feces,  since  no  considerable  amount  of  nitro- 
gen or  mineral  matter  is  believed  to  be  excreted  in  any  other  form. 
When  the  balance  of  carbon,  wath  or  without  oxygen  and  hydrogen,  is 
determined,  the  products  of  respiration  and  perspiration  must  be  taken 
into  account  in  addition  to  the  urine  and  feces.  Experiments  of  this 
nature  are  commonly  called  "respiration  experiments."  The  experi- 
ments reported  here  are  respiration  experiments,  devoted  especially  to 
the  determination  of  the  income  and  outgo  of  nitrogen  and  carbon. 

iThe  residues  of  digestive  juices  and  other  so-called  metabolic  products  of  the 
feces  are,  it  is  true,  a  part  of  the  material  which  has  been  digested,  absorbed,  and 
metabolized,  but  they  represent  material  which  is  neither  utilized  for  building  or 
repairing  organs  or  tissue,  nor  consumed  to  yield  energy,  and  which,  therefore,  may 
here  be  classed  with  the  undigested  residue  of  the  footl. 


9 

Investigation  regarding  the  metabolism  of  matter  in  animals  and 
man  Las  been  very  active  during  the  last  forty  and  especially  tbe  last 
twenty  years.  Indeed  the  experimental  results  already  obtained  in 
this  direction  are  much  more  extensive  than  is  commonly  supposed. 
A  compilation'  has  recently  been  prepared  by  this  office  whicli  it  is 
believed  includes  the  greater  part  of  the  experiments  with  man  and 
the  lower  animals  in  which  the  balance  of  income  and  outgo  of  one  or 
more  chemical  elements  has  been  determined.  Tlic  nnnd)er  of  experi- 
ments in  which  the  income  and  outgo  of  energy  has  been  measured  is, 
however,  extremely  small. 

A  review  of  this  work  made  it  evident  that  research  upon  nutrition 
liad  reached  a  point  where  more  study  of  tlie  ai)plication  of  the  laws  of 
the  conservation  of  matter  and  of  energy  in  the  living  organism  was 
essential.  It  is  not  enough  to  know  the  kinds  and  amounts  of  food 
consumed  as  they  are  shown  by  dietary  studies,  or  the  i)roportions  that 
arc  digested  as  they  are  learned  from  digestion  ex])eriments,  or  the 
general  effects  of  food  materials  as  they  are  brought  out  by  ordinary 
feeding  trials.  Exi)eriments  in  which  the  balance  of  income  and  outgo 
of  nitrogen  are  learned  by  weighings  and  analyses  of  food  and  of  the 
secretions  of  the  kidnej^s  and  intestine  are  extremely  useful,  but  never- 
theless inadequate.  The  balance  of  income  and  outgo  of  the  body  must 
l)e  deterniined  both  in  terms  of  matter  and  of  energy.  For  this  pur- 
pose a  respiration  ai)paratus  which  measured  only  the  income  aiul  outgo 
of  matter  would  not  suffice.  There  was  need  of  an  apparatus  in  whicli 
an  animal  or  a  man  may  be  placed  for  a  number  of  hours  or  days  and 
tlie  amounts  and  composition  of  the  food  and  drink  and  inhaled  air,  the 
amounts  and  composition  of  the  excreta  (solid,  liquid,  and  gaseous),  the 
])Otential  energy  of  the  materials  taken  into  the  body  and  given  off 
from  it,  the  (piantity  of  heat  radiated  from  the  body,  and  the  mechani- 
cal equivalent  of  the  muscular  work  performed  could  all  be  determined. 

Kesi)irati<m  apparatus  of  various  sorts  have  been  devised  by  a  niiin- 
l»er  of  investigators.  They  may,  perhaps,  for  (!onvenieii(;e,  be  divided 
into  three  classes:  (1)  Those  in  which  the  subject  remained  in  a  closed 
chamber  and  was  su])plied  with  oxygen  to  take  the  jilace  of  that  witli- 
<Irawn  from  the  air  by  the  processes  of  respiration.  The  air  in  the 
(chamber  was  aiialyz(Ml  at  the  beginning  and  end  of  the  experiment, 
(li)  Those  in  wiiich  the  subject  remained  in  a.  chamber  supplied  with  a 
(Mirrent  of  air  which  was  measured  and  analyzed  as  it  entered  and  left 
tlie  ehandter.  (.'{)  Those!  in  whicdi  the  subject  did  not  icmain  in  a 
ehamher,  hut  was  jn'ovided  with  api)aiatus  wiiich  iiermitted  the  nu^as 
urenient  and  analysis  of  the  inspired  and  expired  air,  and  the  deter- 
mination of  the  respiratory  (piotient.  In  several  instances  the  last  two 
foims  have  been  combined,  ('alorimeters  have  also  been  devised  by 
many  investigators.  These  have  usually  been  combined  with  respira- 
tion apparatus  of  some  form. 

'  U.  8.  Dept.  Agr.,  (Jllicc  of  Experiment  fcitutions  liiil.  45. 


10 

An  excellent  summary  of  the  methods  and  results  of  respiration 
experiments  up  to  about  the  year  1882,  with  descriptions  of  the  apparatus 
employed,  has  been  prepared  by  Zuntz.^  About  the  same  time  a  like 
excellent  account  of  inquiries  regarding  the  income  and  outgo  of  heat 
of  the  body  was  published  by  Eosenthal.^  Since  that  time  numerous 
forms  of  apparatus  have  been  devised  and  a  large  number  of  experi- 
ments have  been  carried  out.  Keports  of  these  are  published  in  the 
various  scientific  journals  and  have,  so  far  as  known,  not  yet  been 
summarized. 

The  apparatus  which  was  used  in  the  present  experiments  differs  in 
its  essential  points  from  that  used  by  other  investigators.  It  consists 
of  a  respiration  apparatus  similar  in  principle  to  that  of  Pettenkofer 
and  Voit,^  which  belongs  to  the  second  class  mentioned  above.  In 
addition  there  are  devices  for  the  measurement  of  the  energy  liberated 
by  the  organism. 

Tor  measuring  and  analyzing  the  incoming  and  outgoing  air,  new 
methods  have  been  devised,  or  the  methods  already  in  use  have  been 
materially  modified.  The  apparatus  for  measuring  the  outgo  of  energy 
is  entirely  original.  Therefore,  though  the  apparatus  resembles  in 
outward  form  the  respiration  apparatus  of  Pettenkofer  and  Voit,  it  dif- 
fers in  so  many  essential  points  that  it  may  be  fairly  termed  a  new 
form,  and  to  it  the  name  respiration  calorimeter  has  been  applied. 

In  the  earlier  experiments  referred  to  above  the  subject  remained  in 
the  apparatus  for  short  x>eriods,  usually  not  more  than  twenty-four 
hours.  In  the  presen't  experiments  the  subject  remained  for  several 
days  inside  the  respiration  chamber. 

THE  EXPERIMENTS   REPORTED   IN   THIS   BULLETIN. 

The  purpose  of  the  present  article  is  to  give  a  description  of  the 
apparatus  used  and  of  the  methods  which  have  been  elaborated, 
together  with  an  account  of  the  experiments  thus  far  made  by  the 
authors  which  bear  directly  upon  the  metabolism  of  matter.  Four 
experiments  with  men  in  which  the  metabolism  of  nitrogen  and  carbon 
has  been  measured  are  described.  The  results  obtained  regarding  the 
metabolism  of  hydrogen  and  energy  are  to  be  withheld  until  some 
changes  which  experience  has  indicated  to  be  desirable  in  the  appa- 
ratus and  methods  can  be  made,  and  the  results  already  obtained  can 
be  verified  and  new  ones  added. 

The  four  experiments,  designated  by  the  laboratory  numbers  1,  2,  3, 
and  4,  were  as  follows : 

No.  1.  An  experiment  of  fifty-four  hours  with  a  laboratory  assistant. 

No.  2.  An  experiment  of  fifty-four  hours  with  a  laboratory  assistant. 

'Hermann's  Handbuch  der  Physiologie,  vol.  4,  pt.  2,  pp.  86-162. 
^Handbuch  der  Physiologie,  vol.  i,  pt.  2,  pp.  289-456. 

^Pettenkofer  and  Volt's  apparatus  and  a  number  of  experiments  made  with  it  are 
described  in  U.  S.  Dept.  Agr.,  Of6ce  of  Esperinieut  Stations  Bui.  21,  pp.  106-112. 


11 

No.  3.  An  experiment  of  five  days  with  a  clieraist. 
iSTo.  4.  An  experiment  of  twelve  days  with  a  physicist. 
Several  previous  experiments,  which  were  less  complete,  are   not 
reported  here. 

APPARATUS. 

The  first  requisite  for  metabolism  experiments  of  the  kind  here 
reported  is  of  course  reliable  methods  and  apparatus  for  the  accurate 
determination  of  the  different  ftictors  of  income  and  outgo  during  a 
given  period.  This  subject  received  much  painstaking  thought  and 
care  in  the  present  investigation.  The  fact,  however,  should  be  empha- 
sized that  although  these  experiments  were  carried  out  with  much 
attention  to  detail  and  accuracy,  they  are  regarded  simply  as  prelim- 
inary to  more  elaborate,  comprehensive,  and  exact  investigations  with 
improved  apparatus. 


Fid.  1.— Ucsiiiration  ciiliDiiiictor. 

The  apparatus  used  in  tlie  experiments  herewith  reported  consists 
es.srnf  ially  of  a  resi)irafion  clianib(>r  in  wliich  the  subject  stays  daring 
th<;  cxperiinent,  appliances  for  maintaining  a  current  of  air  through 
the  respiration  cliainbcr  for  ventilation,  api)aiatns  for  measuring  and 
iinalyzing  this  ventilating  cuirent  of  air,  and  ajjpliances  for  measnring 
the  heat  given  off  from  the  body  (see  fig.  1). 

Th(i  appiiratns  and  methods  for  tln^  measurement  of  the  heat  given 
off  from  the  body,  which  were  d«;vised  by  Piof.  I*:.  r>.  K'osa,  are  lu'lieved 
to  be  (piite  novel.     The  experience  gained  in  the,  ns<',  of  these  ai>plianc(^s 


12 

has  naturally  suggested  improvements  in  the  details.  The  description 
of  this  part  of  the  apparatus  is  reserved  for  publication  after  the  inves- 
tigations have  further  progressed. 

The  room  in  which  the  apparatus  is  situated  and  in  which  the  larger 
part  of  the  work  of  the  experiment  is  carried  on  is  in  the  basement 
of  the  Orange  Judd  Hall  of  Natural  Science  and  is  a  part  of  the  chem- 
ical laboratory  of  Wesleyan  University.  It  is  35^  feet  long,  20  feet 
wide,  and  9  feet  high;  well  ventilated;  supplied  with  gas,  water,  and 
electricity,  and  heated  by  steam.  During  the  period  of  the  experi- 
ments, which  was  in  late  winter,  the  steam  heat  was  insufficient  for 
comfort  during  part  of  the  night  and  gas  stoves  were  used  in  addition. 
As  the  building  is  of  sandstone,  with  very  heavy  walls,  the  fluctuations 
of  temperature  within,  especially  in  the  basement,  are  comparatively 
slow.  Light  is  su])plied  by  five  large  windows,  and  by  gas  and  elec- 
tricity. A  Vj  kilowatt  motor,  connected  \\ith  convenient  shafting,  fur- 
nishes the  power. 

Opening  out  of  this  room  is  a  smaller  one,  5  by  11^  feet,  fitted  with 
arrangements  for  cooking  the  food.  It  also  serves  as  a  dressing  room 
for  the  snbject  at  the  times  of  entering  and  leaving  the  resijiratiou 
chamber. 

THE   RESPIRATION   CHAMBER. 

The  respiration  chamber  is  a  room  or  box  in  wliich  a  man  may  live 
comfortably  during  the  period  of  an  experiment.  The  inside  dimen- 
sions are:  Length,  2.15  meters;  width,  1.22  meters;  height,  1 .92  meters. 
It  is  provided  with  conveniences  for  sitting,  sleeping,  eating,  and 
working,  as  well  as  arrangements  for  ventilation  and  for  the  study  of 
the  respiratory  products.  The  chamber  consists,  in  fact,  of  three  con- 
centric boxes,  the  inner  one  of  metal  and  the  two  outer  ones  of  wood. 

The  inner  box,  of  which  the  inside  dimensions  have  just  been  given, 
is  donble  walled,  the  inner  wall  being  of  sheet  copper,  the  outer  of 
sheet  zinc.  The  two  walls  are  8  centimeters  apart.  This  double-walled 
box  is  held  in  shape  by  a  wooden  framework  between  the  two  metal 
walls.  The  four  vertical  corners  are  rounded,  as  this  simplifies  the 
construction  and  makes  tlie  apparatus  rather  more  convenient  for  use. 
The  inside  volume  is  approximately  4.8  cubic  meters  (see  figs.  2  and  3). 

An  opening  in  the  front'  end  of  the  metal  chamber,  70  centimeters 
high  and  49  centimeters  wide,  serves  both  the  purpose  of  a  window 
and  a  door  for  entrance  and  exit.  Considerable  dilficulty  was  experi 
enced  in  securing  an  air-tight  closure  for  this  door.  After  numerous 
unsuccessful  experiments  with  frames  of  wood  and  metal  and  with  India 
rubber  gaskets  and  other  appliances,  the  simpler  plan  was  adopted  of 
using  a  large  pane  of  glass  in  a  frame  as  is  done  in  ordinary  windows 

1  In  these  descriptions  the  end  in  which  the  window  is  situated  is  called  the  front. 
The  terms  right  aiul  left  are  applied  to  the  sides  nt  the  right  and  left  of  a  person 
standing  outside  at  the  front  end  and  faciuji-  the  window. 


13 


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H  ::^  ?  ?  ;^  K  9  3:  >-  ^: 


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14 

and  securing  it  with  putty.  The  hxbor  of  putting  the  glass  in  at  the 
beginning  and  taking  it  out  at  the  end  of  an  experiment  is  very  small, 
and  the  plan  serves  the  purpose  admirably. 

Outside  of  this  double- walled  metal  box  are  casings  of  wood.  The 
outer  wooden  walls  are  supplied  with  glass  doors  turning  on  hinges 
and  facing  the  doors  in  the  metal  box. 

The  jnirpose  of  the  double  metal  Avail  of  the  inner  chamber  and  of 
tlie  wooden  casings  is  to  facilitate  the  use  of  the  devices  for  measure 
ments  of  heat.    The  chief  use  of  these  latter  devices  is  in  connection 
witli  the  experiments  to  determine  the  income  and  outgo  of  energy, 
which  are  not  yet  complete  for  publication. 

Numerous  passages  through  the  walls  are  needed  for  tubes,  to  convey 
the  ventilating  current  of  air  and  for  a  current  of  water  to  carry  off  the 
heat  generated  by  the  body  of  the  occupant  of  the  chamber,  wires  for 
various  electric  connections,  metal  rods  for  certain  connections  between 
the  interior  and  exterior  apparatus,  and,  finally,  the  "food  tube"  for 
passing  the  food  and  drink  into  the  apparatus  and  taking  out  the  solid 
and  liquid  excretory  products.  The  tubes  referred  to  are  of  various 
sizes  and  made  of  either  brass  or  copper.  The  "ventilating  tubes" 
have  an  internal  diameter  of  4  centimeters.  The  food  aperture  is  of 
copper  and  has  an  internal  diameter  of  15  centimeters.  It  is  situated 
on  the  left  side  of  the  apparatus,  and  is  provided  with  a  cap  at  each 
end.  The  outer  cap  is  attached  by  a  screw  so  that  it  may  be  made  air- 
tight. In  putting  in  the  food  and  other  materials  the  cap  is  taken  off", 
the  receptacle  containing  the  food  is  placed  in  the  tube  and  the  cap  put 
on  again.  A  signal  is  then  given  to  the  man  inside  who  removes  the 
inner  cap  and  takes  out  the  receptacle.  The  materials  from  within  are 
passed  out  in  corresponding  manner.  In  this  way  there  is  no  danger 
of  ingress  or  egress  of  any  considerable  quantity  of  air. 

A  telephone  furnishes  a  means  of  communication  between  the  inside 
and  outside  of  the  chamber;  the  wires  of  the  telephone  pass  through 
rubber  stoppers  inserted,  in  a  tube,  which,  in  its  turn,  passes  through 
all  of  the  boxes  and  walls  and  is  soldered  to  the  inner  copper  wall. 
Other  wires  through  the  same  tube  provide  for  electrical  connection 
with  a  small  bell  on  the  outside  so  that  the  i^erson  within  may  call  an 
attendant  whenever  desired. 

Adequate  provision  is  made  for  the  ventilation  of  the  chamber  and 
for  maintaining  a  uniform  humidity  and  temperature  by  means  of  the 
appliances  described  below  (p.  16).  An  inconvenient  rise  of  tempera- 
ture is  prevented  by  a  current  of  cold  water  which  passes  through  a 
system  of  pipes  inside  of  the  chamber.  This  device  forms  a  part  of 
the  arrangements  for  measuring  the  heat  given  off"  from  the  body.  As 
the  results  of  such  measurements  are  not  reported  in  this  article,  it  will 
suffice  to  say  that  the  plan  followed  is  in  fact  the  opposite  of  that  used 
in  heating  houses  by  hot  water  radiators,  i.  e.,  instead  of  passing  hot 


15 


K  b  p  -  > 

"^  >  '£■  '^'  'ii, 

■-I   —  _   p   3 


e^  w  K  9  ^ 
^  ^  1-  -^  O 

£^   ?  5   2   3 


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P    t2)   ^ 


S    K    b 
M-    3     S     o 


a.  W  'p 


■n  Z] 


16 

water  tliiougli  radiators  to  give  off  heat  for  warming  the  air,  cold  water 
is  passed  through  absorbers  to  remove  heat  from  the  air. 

A  wet  and  dry  bulb  hygrometer,  capable  of  being  read  to  tenths  of 
a  degree  centigrade,  is  hung  in  the  rear  of  the  chamber  and  observa- 
tions w^ere  made  by  the  occupant,  generally  at  intervals  of  two  hours, 
during  the  period  of  the  experiment.  These  observations  were  reported 
by  the  telephone  and  show  the  hygrometric  condition  of  the  air  inside 
of  the  apparatus. 

The  furniture  used  in  the  experiments  consisted  of  a  light  folding 
canvas  cot  bed,  a  folding  chair,  and  a  folding  table.  Such  clothing  and 
bedding  as  were  needed  for  comfort  Avere  taken  in  by  the  man  at  the 
beginning  of  the  experiment,  and  small  articles  were  passed  in  and  out 
through  the  food  tube  at  convenient  times.  Tlie  floor  was  protected  by 
carpeting.  The  amounts  of  water  held  by  the  furniture  and  clothing, 
etc.,  were  determined  as  accurately  as  practicable  by  weighings  at  the 
beginning  and  end  of  each  experiment. 

The  arrangements  for  measuring  and  sampling  the  air  are  described 
as  they  were  actually  used  iu  the  experiments.  They  have  since  been 
replac  ed  by  others  which  will  be  described  with  accounts  of  experi- 
ments now  in  i^rogress. 

APPLIANCES  FOR  VENTILATION  AND  FOR  THE  MKASUREMENT  AND 
ANALYSIS  OF  THE  VENTILATING  CURRENT  OF  AIR. 

A  satisfactory  respiration  experiment  involves  the  maintenance  of  a 
proper  current  of  air,  the  accurate  measurement  of  its  volume,  and  the 
determination  of  the  respiratory  products.  When  a  living  subject  is 
in  the  respiration  chamber  and  breathes  its  air  it  is  essential  that  the 
ventilation  be  sufficient  for  his  comfort,  but  it  is  important  that  the 
amount  passed  through  the  chamber  be  not  too  large,  on  account  of 
the  difliculty  of  accurate  measurement  and  analysis.  With  a  small 
current  the  reasonably  accurate  measurement  of  the  volume  is  easier 
than  with  a  large  one,  smaller  samples  are  needed  for  analysis,  and  the 
samples  can  be  taken  and  the  analyses  made  more  accurately. 

It  is  evident  that  the  greatest  care  is  needed  to  devise  such  mechan- 
ism and  methods  as  will  secure  the  maximum  at-curacy  of  measurement 
and  sampling  of  the  air  and  of  determination  of  the  respiratory  prod- 
ucts. In  the  large  amount  of  work  done  during  the  last  thirty  years 
with  various  modiiicatious  of  the  Pettenkofer  apparatus  the  chief  diffi- 
culties have  been  iu  the  measurement  of  the  air  and  determinations  of 
the  water.  The  method  generally  followed  has  been  to  measure  both 
the  total  volume  of  air  and  the  volume  of  the  samples  by  gas  meters, 
and  to  use  the  samples  for  determining  the  carbon  dioxid  and  water  by 
absorption  and  the  marsh  gas  and  other  volatile  organic  comi^ounds 
by  combustion. 

The  same  general  method  has  been  followed  in  these  experiments. 
The  air  was  drawn  through  the  apparatus  by  means  of  si^ecially  devised 


17 


jiir  i)iiini)s,  and  its  total  vuluiue  measured  by  ii  gas  meter  especially 
constructed  for  the  i)urpose.  The  samples  of  incoming  and  outgoing  air 
were  drawn  by  means  of  aspirators,  the  carbon  dioxid  in  the  sample 
was  determined  by  absorption  by  soda  lime,  and  the  water  by  absorp- 
tion by  sulpliuric  acid. 

As  the  air  was  drawn  and  not  forced  through  the  apparatus,  and 
especial  pains  were  taken  to  make  both  the  respiration  chamber  and 
the  connecting  pipes  as  nearly  air-tight  as  possible,  it  was  believed 
that  the  air  which  passed  through  the  meter  and  was  measured  by  it 
represented  very  accurately  that  wliich  had  passed  through  the  cham- 
ber and  received  the  juodncts  of  respiration.  It  is  not  certain  that  the 
chamber  was  absolutely  air-tight,  but  at  no  place  could  any  current  of 
incoming  air  other  than  that  passing  through  the  entrance  and  exit 
tubes  be  found  sufficient  to  affect  the  ilamc  of  a  candle.  Indeed,  it  was 
hardly  ex]K'cte(l  that  any  considerable  <|uaiitity  of  air  could  enter  or 
pass  out  in  any  other  way  even  if  the  chamber  had  not  Ijeen  tight,  since 


Fli;.  t. — Oiitliiii'  .skclrli  of  icsiiiratidii  ;i]i])ar;i(ii.s. 

the  tension  within  the  chamber  was  very  slight,  the  barometric  pres- 
sure differing  from  that  of  the  outside  air  by  only  a  fraction  of  a  milli- 
meter of  mercury.  The  volume  of  air  passing  through  the  apparatus 
varied  from  50  to  1~>  liters  jx'r  minute.  The  longest  experiment  was  of 
twelve  days'  duration,  and  was  made  with  an  air  current  of  approxi- 
mately 55  liters  per  minute. 

It  is  desiralde  to  have  the  incoming  current  of  air  as  dry  as  i)ossible, 
as  stated  above.  The  smaller  and  more  uniform  the  amounts  of  water 
the  easier  and  more  accurate  are  the  analytical  deteniiinations,  and, 
birtheiiuore,  the  amount  of  ventilation  needed  for  the  comfort  of  the 
ofcnpant  of  the  (jhamber  is  less  with  little  than  with  much  moisture. 
To  redu<;e  tin;  amount  to  aininimum  the  air  which  caitiC  from  out  of 
doorB  was  dried  before  it  entered  the  chamber.  This  drying  was  easily 
accomplished  by  surrounding  a  portion  of  tin;  pi[)e  through  which  it 
passed  with  a  freezing  mixture  of  salt  and  ice. 
U771_]So.  11 2 


18 

The  course  of  the  air  in  its  passage  from  outside  through  the  diiferent 
parts  of  the  apparatus  to  the  pumps  was  as  follows  (see  fig.  4) :  It  entered 
through  a  window  by  a  pipe  of  7.5  centimeters  internal  diameter  and 
was  drawn  through  a  freezer  (Ej)  consisting  of  a  system  of  10-centimeter 
copper  pipes  packed  in  ice  and  salt;  thence  it  was  again  conveyed  by  the 
7.5  centimeter  air  pipe  (Dj)  to  the  smaller  air  pipe  which  passes  through 
the  front  wall  of  the  apparatus  at  the  right  of  the  window  (B)  and  about 
1.2  meters  from  the  bottom  of  the  chamber  (A).  In  its  passage  from  the 
freezer  to  the  chamber  it  was  warmed  so  that  it  entered  the  latter  at 
the  desired  temperature.  The  warming  was  done  by  a  16  candlepower 
incandescent  electric  lamp  placed  inside  the  air  pipe.  In  this  way  the 
temperature  of  the  entering  current  of  air  was  easily  regulated.  The 
air  entering  the  chamber  makes  a  direct  downward  turn  through  a  cop- 
per pipe  10  centimeters  in  diameter  which  opens  into  the  lower  right- 
hand  front  corner  of  the  chamber.  Tlie  outgoing  air  is  drawn  from  the 
upper  left-hand  corner  of  the  rear  end  of  the  chamber,  i.  e,,  from  a  point 
diagonally  opposite  that  at  whicli  the  incoming  air  is  delivered.  It  is 
conveyed  from  the  latter  i^oint  by  a  lO-centimeter  copper  tube  along 
the  top  of  the  chamber  to  tlie  front  end  and  then  downward  to  the 
copper  tube  (1)2)  through  which  it  passes  out.  In  this  way  a  favorable 
distribution  of  the  air  in  the  chamber  is  obtained.  Tlie  diameter  of  the 
brass  tubes  has  proven  ample  for  the  uninterrui:)ted  passage  of  such 
currents  of  air  as  liave  been  found  desirable  for  the  experiment.  On 
coming  out  of  the  chamber  the  ventilating  current  of  air  was  passed 
through  another  freezing  apparatus  (E2)  by  which  the  larger  part  of  the 
moisture  was  collected.  Thence  it  passed  through  the  meter  (F)  by 
which  its  volume  was  measured  and  onward  to  the  air  pump  (H).  Since, 
however,  the  action  of  the  pump  would  vary  the  tension,  a  tension 
equalizer  (G)  was  placed  between  the  pump  and  the  meter. 

Samples  of  the  incoming  air  were  taken  from  the  entrance  pipe  just 
as  it  entered  the  chamber.  Samples  of  the  outgoing  air  were  likewise 
taken  from  the  exit  pipes  just  as  it  entered  the  meter. 

The  several  parts  of  this  apparatus  for  maintenance  and  meas.uring 
the  current  of  air  may  be  described  in  more  detail  as  follows : 


Two  piston  pumps  were  used  for  drawing  the  air  tbrough  the  appa- 
ratus. They  were  so  arranged  that  either  could  be  used  alone  for  a 
smaller  current,  or  the  two  together  for  a  larger  current.  In  most  of 
the  experiments  here  described,  however,  only  one  pump  was  used. 
The  piston  of  each  pump  was  moved  in  a  brass  cylinder  by  cranks  at 
the  end  of  a  shaft,  so  that  each  pump  made  a  double  stroke  for  each 
revolution  of  the  shaft.  This  shaft  was  belted  to  the  main  shaft,  which 
works  directly  from  the  motor,  and  runs  at  the  rate  of  about  300  revolu- 
tions per  minute.  The  connections  were  such  that  the  pump  made  in 
general  about  75  strokes  per  minute.    The  strokes  were  recorded  by  an 


19 

ordinary  autouiatic  register  reading  to  100,000.  As  the  volume  of  air 
l»er  stroke  was  known  approxinuitely  this  record  made  a  rough  check 
upon  the  uieasureinents  with  the  meter.  Desirabh;  changes  in  the  rate 
of  How  of  air  thiough  the  puni})  are  effected  by  varying  the  length  of 
tlic  stroke.  tUe  devices  for  this  i)urpose  being  such  that  the  desired 
clianges  could  be  made  with  ease  and  accuracy.  When  one  of  the 
pumps  drew  Co  liters  per  miuute  each  stroke  represented  approximately 
0.7  liter. 

TKNSION    Ei^l  ALIZEK. 

When  the  [luiiips  were  connected  directly  with  the  meter  the  motion 
of  the  latter  was  intermittent  on  account  of  the  variations  in  air  pres- 
sure with  each  stroke  of  the  ]»uinp.  To  reduce  these  variations  of 
tension  to  a  minimum  and  make  the  i)ressare  of  the  air  as  it  passed 
through  Ihe  meter  more  unitbrm  a  device  was  employed  to  which  the 
name  tension  equalizer  was  given.  This  was  placed  so  that  the  air 
passed  through  it  in  going  from  the  meter  to  tlie  pump.  It  consists  of 
a  cylinder  about  50  centimeters  high  and  40  centimeters  in  diameter. 
The  sides  and  bottom  of  this  are  of  tin  plate.  Over  the  top  a  piece  of 
rubl)er  sheeting,  such  as  is  used  by  dentists,  is  loosely  stretched  and 
tightly  bound.  Although  its  capacity  is  only  between  50  and  00  liters, 
yet  the  action  of  the  rubber  top  was  such  that  the  variation  in  pressure 
of  the  meter  as  measured  by  a  water  column  amounted  to  only  a  few 
millimeters,  and  no  irregularity  could  be  seen  in  the  motion  of  the 
index  ou  the  meter. 

METE II  EOK  MEASURING   AIR. 

The  meter'  was  of  the  kind  employed  by  Professor  Zuntz,  of  the 
Agricultural  Institute  of  the  University  of  Berlin,  in  his  respiration 
exi)eriments  with  horses,  dogs,  and  other  animals,  and  with  man.  Pro- 
fessor Zuntz  was  so  kind  as  not  only  to  assist  in  getting  the  meter,  but 
also  to  test  it  in  his  laboratory.  The  apparatus  has  been  brietiy 
described  by  Professor  Zunt/.,'-  and  only  the  essential  features  will  be 
noticed  here. 

The  readings  of  the  nu;ter  are  indicated  by  hands  revolving  on  a 
large  dial  and  recording  to  10,000  liters.  In  the  experiments  the  meter 
is  read  for  the  number  of  thousands  of  liters,  while  the  numbers  often 
thousands  of  liters  were  checked  by  the  register  above  referred  to 
uinler  the  head  of  "Air  pump"  (]>.  18). 

The  accuiacy  of  measurements  of  volumes  of  air  by  a  gas  meter  has 
l)ecn  a  subject  of  much  discussion  aud  no  little  experimenting,  and  the 
attention  given  to  it  in  this  laboratory  has  been  not  inconsiderable. 
The  errors  involved  are  undoubtedly  small,  and  with  care  may,  it  is 
believed,  be  reduced  to  a  very  small  fraction  of  the  total  volume  of  air 
to  be  measured. 


'Maili-  by  S.  KlHt.r,  <if  ]{.  rlin. 

■"Liindw.    .Jiihrb.,   IS  (ISSO;,    p.    1;    :i1h<)    l''lii;,';L,'o,     llygii;iii,s(lic     lJiit.i8U(luiii<,'8- 
mi;tlio<leii,  p.  DiJl. 


20 

In  using  the  meter  a  thermometer  was  inserted  at  one  side,  so  that 
its  bulb  was  immersed  in  the  water  within  the  meter  and  its  readings 
were  taken  as  indicating  the  temperature  of  the  water.  This  was 
assumed  to  be  also  the  temperature  of  the  air  as  it  left  the  water.  The 
air  was  assumed  to  be  saturated  with  aqueous  vapor  at  that  temjjera- 
ture.  As  the  air  passed  through  at  the  slow  rate  of  from  55  to  80  liters 
per  minute,  it  was  not  believed  that  this  assumption  involved  a  very 
large  error.  It  was  believed,  however,  tliat  means  (tould  be  found  by 
which  the  errors  of  measurement  could  be  materially  reduced.  An 
apparatus  for  the  purpose  has  been  devised  and  made  by  Mr.  O.  S. 
Blakeslee,  and  the  preliminary  observations  made  with  it  are  quite  sat- 
isfactory. It  is  practically  a  large  mercury  pump,  so  arranged  as  to 
serve  the  double  purpose  of  maintaining  the  current  of  air  and  deliver- 
ing aliquot  samples  for  analysis. 

ASPIRATORS   FOR    SAMPLING   AIR. 

The  samples  of  air  for  analysis  were  drawn  by  means  of  aspirators  (I). 
These  aspirators,  three  in  number,  are  cylinders  of  galvanized  iron, 
standing  upright,  with  conical  ends.  The  cylinders  are  50  centimeters 
in  diameter  and  40  centimeters  in  height,  exclusive  of  the  cones  which 
form  the  ends.  The  cones  are  approximately  8  centimeters  in  height, 
making  the  whole  length  of  the  cylinder,  from  apex  to  apex,  about  02 
centimeters.  At  the  apex  of  each  cone  is  a  short  neck  of  brass  tubing. 
Horizontal  tubes  connect  the  two  necks  with  an  upright  glass  tube  ou 
the  side  of  the  asi)irator.  This  serves  as  a  gauge  and  shows  the  height 
of  the  water.  It  is  accurately  marked  at  the  top  and  bottom,  and  thus 
permits  the  drawing  off  of  a  detinit(i  quantity  of  water  and  consequently 
the  accurate  measurement  of  the  volume.  The  aspirators  are  sustained 
in  a  framework  and  set  in  cement  to  give  them  hrm  support.  At  the  top 
of  each  is  a  3-way  valve,  Avhich  serves  to  make  connections  with  the 
tubes  (Ki  and  IC,)  bringing  the  samples  of  air.  A  manometer  indicates  the 
tension  and  a  thermometer  the  temperature  of  the  air  in  the  as[)irators. 
Here  again  the  air  was  assumed  in  the  experiments  to  be  saturated  at 
tlie  temperature  indicated  by  the  thermometer.  The  volume  of  water 
or  air  held  by  each  of  these  aspirators  was  determined  by  weighing  the 
water  which  it  held,  and  was  from  150  to  103  liters.  The  connection 
between  the  aspirators  aud  the  tubes,  through  which  the  main  current 
of  air  passes,  was  made  by  0-ceutimeter  brass  tubes.  The  sample  cur- 
rents of  air  are  brought  from  the  main  air  current  through  these  small 
brass  tubes  into  the  apparatus  for  the  absorption  of  carbon  dioxid  and 
water  (Li  and  La)  and  then  into  the  aspirators,  by  which  the  samples 
are  drawn  and  the  volume  of  each  sample  is  measured. 

The  rate  of  iiow  is  regulated  in  a  very  simple  manner.  The  water 
passes  out  from  the  bottom  of  the  aspirators  through  a  short  brass 
tube  which  is  connected  with  a  longer  rubber  tube.  Thelast  is  provided 
with  a  screw  pinchcock  and  a  metallic  nozzle  at  the  lower  end,  which 


21 

is  riised  or  lowered  at  will,  thus  vaiyiiiji  the  head  of  water.  In  tak- 
ing; a  sample,  the  aspirator  is  first  filled  to  the  mark  indicated  on  the 
winter  gauge  outside.  The  connection  is  made  by  the  3  way  cock  with 
the  tube  through  which  the  sample  of  air  is  drawn  from  the  main  cur- 
rent. The  flow  of  water  from  the  bottom  is  started  with  the  nozzle  at 
the  end  of  the  rubber  tube  at  the  height  of  about  1  meter  from  the  floor. 
The  water  which  first  comes  out  is  collected  in  a  graduated  cylinder. 
The  amount  in  one  minute  shows  the  rate  of  flow.  If  this  is  too  fast  or 
too  slow,  it  is  changed  by  means  of  the  pinchcock  on  the  rubber  tube. 
AVhen  the  i)roi)er  flow  is  established,  ordinarily  about  500  or  (iOO  cubic 
centimeters  per  minute,  it  is  allowed  to  proceed.  As  the  water  level  in 
the  aspirator  falls,  the  nozzle  is  lowered  and  the  rate  of  flow  is  observed 
at  intervals,  generally  of  about  one  half  hour.  In  this  way  it  is  easy  to 
make  the  rate  rapid  or  slow  at  discretion  and  reasonably  uniform. 

AITARATUS    FOR    DETERMINING    CARBON    DIOXID    AND    WATER   IN    SAMPLES    OF    AIR. 

The  constituents  of  the  air  determined  in  the  experiments  described 
beyond  were  carbon  dioxid  and  aqueons  vapor,  although  only  the  for- 
mer is  reported.  The  device  above  referred  to  (p.  17)  for  removing  the 
moisture  from  the  main  air  current  by  cooling  to  about  — 17°  C.  leaves  a 
small  and  fairly  uniform  amount  of  moisture,  and  thus  greatly  facili- 
tates the  determination  of  the  latter  in  the  sam])les  analyzed.  Four 
U -tubes  are  used  for  the  analysis,  two,  filled  with  soda-lime,  for  the 
carbon  dioxid,  and  two,  containing  sulphuric  acid,  for  the  water  of  each 
saniple.  For  weighing  they  are  hung  by  loops  of  platinum  or  aluminum 
wire. 

Freezing  apparatun. — It  was  found  very  desirable  in  these  experi- 
ments to  have  the  air  enter  the  respiration  chamber  as  dry  as  possible. 
It  was  with  this  fa(;t  in  view  that  the  ])lan  was  first  adoi>ted  for  freez- 
ing the  air  before  it  entered  the  chamber.  The  freezer  used  for  this 
purpose  consists  practically  of  two  large  U -tubes  of  copper.  These  are 
(;onnected  with  each  other  and  with  the  i)iiie  through  which  the  current 
of  incoming  air  lh)ws.  They  stand  upright  in  a  wooden  box  which  is 
ke])t  filled  with  a  freezing  mixture  of  salt  and  ice.  Fach  of  the  four 
ui)rights  of  the  two  U-tubes  consists  of  a  pipe  made  of  (No.  1(5)  sheet 
(•o])per,  10  ccntinieters  in  diameter  and  01.4  centimeters  in  length. 
These  ui)right  pipes  are  so  connected  by  horizontal  elbows  that  the 
whole  forms  a  compact  mass  1  meter  in  length  and  a  little  over  L'O  cen- 
timeters s(|uare.  In  this  way  the  current  of  air  has  to  ]>ass  through 
neaily  '.'>Mr>  meters  of  cojjper  tubing  which  is  covered  by  the  i'wv/Aug 
mixture.  To  still  further  increase  the  cooling  surface  of  metal,  and 
with  it  the  rapidity  of  tlu;  ])assage  of  heat  from  the  air  to  the  freezing 
niixtuH',  a  number  of  vanes  of  she<;(  eopix'i'  are  jthiced  inside  the  lour 
lengths  of  copper  tubing.  lOach  vane  is  parallel  with  the  axis  of  the 
tube  and  is  soldered  to  the  side  so  as  to  |)roJect  .'{.8  centimet(!rs  toward 
tlie  (tenter  in  a  radial  direction.  In  tlu'.  horizontal  elbow  througli  wiiich 
tlie  air,  after  lia\ing  jtassed  through  (he  lour  tubes,  returns  to  the  main 


22 

conducting  pipe  is  an  orifice  in  which  is  inserted  a  thermometer.  This 
indicated  the  temperature  of  the  air  as  it  left  the  freezer,  under  ordinary 
conditions  to  be  from  about  — 17°  to  — 18°  0.  The  wooden  box  which 
held  the  freezing  mixture  and  the  freezing  apparatus  had  at  the  bottom 
an  outlet  for  the  brine.  The  ice  was  finely  crushed,  mixed  with  salt, 
and  packed  closely  between  the  freezer  and  the  box. 

When  the  experiment  was  continued  for  twelve  days,  the  moisture 
which  gathered  in  the  form  of  frost  on  the  inside  of  the  freezing  appa- 
ratus accumulated  so  as  to  retard  the  passage  of  the  current.  Accord- 
ingly the  pump  was  stopped  in  the  middle  of  the  experiment,  the 
freezer  taken  out,  and  hot  water  poured  upon  it  so  as  to  melt  the  ice 
inside.  It  was  then  emptied,  put  back  in  place,  and  repacked  in  the 
freezing  mixture.  The  whole  operation  did  not  last  more  than  twenty 
minutes.  The  stoppage  of  the  current  of  air  during  this  time  did  not 
cause  the  least  discomfort  to  the  person  inside  the  chamber.  Indeed, 
he  was  not  aware  of  it  until  he  was  told. 

It  was  found  necessary  to  repack  the  space  outside  the  freezer  with 
ice  and  salt  about  once  in  two  hours  under  ordinary  conditions.  This 
method  of  removing  the  excess  of  moisture  from  the  air  before  it  enters 
the  chamber  proved  so  satisfactory  as  to  lead  to  its  adoption  in  quanti- 
tative determinations  of  the  moisture  in  the  outgoing  air.  For  this 
purpose,  however,  a  somewhat  more  complicated  freezer  is  necessitated 
by  the  fact  that  the  water  which  it  collects  must  be  accurately  weighed. 
The  detailed  description  of  this  freezer  is  reserved  for  future  publi- 
cation. 

Objections  to  the  use  of  ice  and  salt  for  freezing  are  the  trouble  of 
frequent  renewal,  the  expense  for  material  and  labor,  which  was  not 
inconsiderable,  the  difficulty  of  getting  a  satisfactory  low  temperature, 
and  especially  the  impossibility  of  maintaining  a  constant  tempera- 
ture. For  the  later  experiments  immersing  the  freezers  in  brine  cooled 
by  the  expansion  of  ammonia  gas  has  been  adopted.^ 

METHODS  OF  SAMPLING  AND  ANALYSIS. 
ANALYSIS   OF  FOOD,  FECES,  AND  UEINE. 

The  methods  of  analysis  used  were  essentially  those  adopted  by  the 
Association  of  Oificial  Agricultural  Chemists,  with  such  modifications 
as  exx)erience  and  circumstances  have  shown  to  be  desirable.^ 

PREPARATION   AND   SAMPLING   OF   FOOD. 

In  the  preparation  of  the  food  special  effort  was  made  to  secure  such 
mechanical  condition  of  the  materials  as  would  facilitate  the  most 
thorough  and  accurate  sampling,    The  samples,  when  too  moist  for 

1  The  so-called  "Economical  Ice  Machine,"  made  by  the  Atlantic  Refrigerating 
Comjiauy,  of  Springfield,  Mass.,  has  been  found  very  satisfactory  for  this  purpose. 

2  For  detailed  descriptions  of  the  usual  methods  followed,  with  the  possible  sources 
of  error  involved,  see  U.  S.  Dept.  Agr.,  Division  of  Chemistry  Bui.  46;  Office  of 
Experiment  Stations  Buls.  21,  pp.  39-52,  and  29,  pp.  8,9. 


23 

griiuliiig",  were  partially  dried:  tlie  material  in  the  original  or  partially 
dried  form  was  sampled  and  ground,  first  in  an  ordinary  "Excelsior 
mill,"  afterwards  in  a  Maercker-Dreefs  mill,  by  Avlii(;li  it  is  easily 
reduced  to  a  very  line  powder.  Some  materials,  containing  consider- 
able quantities  of  fat  or  sugars,  are  not  easily  groujid  in  this  way. 
Meats,  eggs,  and  canned  pears,  for  instance,  were  rubbed  in  a  mortar 
until  they  wei-e  homogeneous.  The  ground  material  was  preserved  for 
analysis  in  Tightly  sto])i)ered  bottles.  It  lias  been  found,  however,  that 
when  such  materials  are  keiit  in  bottles  closed  with  glass,  or  even  rub- 
ber stoppers,  they  are  apt  to  change  in  moisture  content  on  long  stand- 
ing. Unless  the  analyses  are  to  be  made  immediately,  or  within  three 
or  four  days  at  longest,  it  is  best  to  seal  glass-stoppered  bottles  with 
parartin.  Even  then,  if  the  material  has  stood  for  some  weeks,  it  will 
sometimes  be  found  desirable  to  repeat  the  determinations  of  moisture. 
When  nearly  all  the  water  is  removed  from  the  materials,  as  is  done  in 
the  process  of  partial  drying  referred  to  beyond  (p.  24),  no  indications 
of  decomposition,  even  of  meats,  Avere  found  for  some  weeks  or  months. 
It  is,  however,  noticeable  that  when  the  samples  of  meats  containing 
more  or  less  fat  are  thus  dried  and  finely  ground,  and  are  allowed  to 
stand  in  the  working  room  of  the  laboratory,  the  fat  gradually  sepa- 
rates ami  settles  to  the  bottom  of  the  bottle.  This  is  an  indication  of 
the  need  of  careful  mixing  of  such  materials  Just  before  the  weighing 
of  portions  for  analysis. 

Some  food  materials,  however,  are  so  dry  as  not  to  require  the  partial 
drying.  Ordinary  fine  wheat  Hour  is  ready  for  analysis  at  once,  or  can 
be  preserved  for  some  time  in  tightly  closed  bottles.  The  coarser  tlours 
and  meals,  rice,  and  common  crackers  and  biscuit  can  generally  be 
ground  and  kept  for  analysis  without  drying. 

Since  in  some  instancies  the  treatment  was  somewhat  detailed,  the 
methods  used  for  the  ])reparation  of  each  kind  of  food  for  analysis  may 
be  brieriy  outlined. 

/>V(9/'. — A  lean  i)iece  of  round  steak  was  selected  and  the  superfluous 
fat  w.as  carefully  removed.  The  meat  was  then  cut  in  long  strips  and 
rnn  thiongh  a  meat  chopper  several  times,  thus  securing  fine  division 
and  thoiough  mixture.  Aftei'  leaving  the  chopper  it  was  weighed  out 
in  balls  or  cakes  of  O'J.l  grams  each,  and  ]>la(;ed  on  a  plate  covered  with 
a  glass  cover.  When  meat  was  cooked  for  a  meal  three  of  these  balls 
were  cooked  at  the  same  time  and  in  the  same  dish;  two  of  them  were 
eaten,  and  tlie  thir<l  served  as  a  sampl(^  for  analysis. 

Ihuad. — Tiiiee  kinds  were  used,  "white  bread,"  made  of  fine  wheat 
Hour;  "brown  bread,"  of  wheat  and  rye  flour  and  corn  meal;  and  rye 
bread.  To  insure  like  composition  and  lik;>  proportions  of  crust  and 
ciiiinb,  the  loaf  was  cn(  in  slices  and  alternate  slices  wer(^  taken  for 
eating  and  analysis. 

Oatmeal. — One  of  the  (;ommon  commercial  pieparations  of  oatmeal 
was  used.  A  cei'tain  weight  of  the  dry  material  was  cooked  in  water. 
Ah  there  was  no  reason  to  fcai'  h)ss  of  material  the  composition  of  the 


24 

oatmeal  as  eaten  was  assumed  from  that  of  the  original  material,  tak- 
ing- into  account  tlie  water  added  in  cooking. 

Potatoes. — These  were  boiled  with  the  skins  on.  After  pouring  off 
the  water  the  skins  were  removed  and  the  potatoes  put  through  a  ])otato 
maslier.  The  portion  to  be  eaten  was  weighed,  a  sample  of  like  weight 
being  taken  at  the  same  time  for  analysis. 

Apples. — The  fresh  fruit  was  pared.  ai5d  the  cores  removed,  notliing 
but  the  apple  pulp  being  eaten  by  the  subject.  Samples  of  the  pulp 
were  analyzed. 

Canned  heans^  pears.,  and  peaches. — Tiiese  three  materials  wore  served 
cold,  and  required  no  special  preparation.  Samples  from  the  different 
cans  were  used  for  analysis. 

Milli  craclcers,  sugar,  and,  cheese. — These  were  served  as  purchased  in 
the  market,  without  any  special  preparation.  Samples  of  each  lot  were 
analyzed. 

Uggs. — Eggs  of  approximately  the  same  weight  were  selected.  Three 
were  boiled  in  the  same  dish  of  water,  two  were  eaten,  and  one  was 
taken  as  a  samjile. 

Butter. — This  was  a  creainery  butter  as  purcliased.  No  partial  dry- 
ing- was  necessary.  Samples  were  taken  at  each  meal,  each  sample 
being  of  the  same  weight  as  the  portion  eaten. 

Milk. — Aliquot  portions  Avere  taken  from  the  milk  of  each  day. 
These  samples  were  preserved  until  analyzed  by  addition  of  potassium 
bichromate. 

As  fast  as  samjiles  were  taken  they  were  either  immediately  '^  partially 
dried,"  as  in  the  case  of  meat,  bread,  potatoes,  etc.,  or  preserved  for  future 
analysis  by  some  antiseptic,  such  as  potassium  bichromate,  as  in  the  case 
of  milk.  The  several  samples  of  a  g-iven  material  for  a.  given  period  were 
joined  together  and  resampled,  so  that  a  single  analysis  served  for  the 
whole  of  that  special  lot.  Thus  the  several  samples  of  "white"  bread 
for  a  given  number  of  days  were  united,  and  after  the  partial  drying 
were  well  mixed  and  a  single  sample  representing  the  whole  was 
analyzed.  This  course  was  followed  with  the  other  materials  in  so  far 
as  it  was  feasible  without  risk  of  inaccuracy. 


Partial  drying. — For  this  process  portions  of  50  grams  each  were 
placed  in  shallow  porcelain  sauce  dishes  and  heated  in  a  large  air  bath 
at  the  usual  temperature  of  90°  0.  or  thereabouts  for  a  period  of  thirty- 
six  hours.  They  were  then  placed  on  a  shelf  lightly  covered  with  paper, 
and  thus  exposed  to  the  air  in  the  laboratory  for  twenty-four  hours. 
At  the  end  of  this  time  the  moisture  content  had  become  practically 
constant  and  the  samples  were  weighed  and  the  loss  of  moisture  noted. 
They  were  then  ground,  placed  in  properly  marked  bottles,  and  set 
aside  for  analysis. 

Complete  drying.— For  the  determination  of  water- free  substance  the 
usual  methods  were  employed.     The  time  of  drying  was  usually  five 


25 

lionrs.  ill  accordance  with  the  official  methods.  This,  however,  did  not 
suffice  ill  all  cases,  and  longer  heating  was  necessary.  It  is  well 
known  that  one  of  the  most  difficult  operations  in  the  laboratory  is  the 
accurate  determination  of  moisture  in  animal  and  vegetable  substances, 
and  not  a  little  work  has  been  done  in  this  laboratory  with  a  view  to 
improving  the  accuracy  of  moisture  determinations.' 

!■■  AT — ETIl  K R    K X T RA CT. 

Tlie  sample  which  had  been  dried  in  hydrogen  for  the  water  determi- 
nation was  used  for  the  determination  of  crude  fat.  To  this  end  it  was 
extracted  in  the  usual  way  with  ether,  which  had  been  digested  with 
fused  calcium  chlorid  and  distilled  over  that  substance.  Continuous 
extraction  for  sixteen  hours  was  generally  sufficient. 


For  determination  of  ash  the  material  was  incinerated  in  tlie  follow- 
ing manner:  The  mass  was  tirst  charred  in  a  platinum  capsule  and 
then  extracted  with  hot  distilled  water,  the  insoluble  matter  being 
collected  on  a  filter;  the  filter  with  its  contents  was  then  returned  to 
the  i)latinum  capsule  and  the  whole  heated  until  the  incineration  was 
conii)lete.  The  aqueous  extract  was  added,  and  after  eva]>oration  the 
whole  residue  was  heated  at  low  redness  until  the  ash  was  white. 

N1T1!<  XiKN — PROTEIN. 

Nitrogen  was  determined  by  the  Kjeldahl  method,  tlie  amount  of 
nitrogen  thus  found  multiplied  by  0,25  being  taken  as  representing  the 
protein.  As  the  proportion  of  nitrogen  is  the  basis  of  the  calculations 
of  nitrogen  bahiuce,  the  method  of  estimating  juoteiu  by  difierences, 
whidi  is  often  followed  in  analysis  of  meats  and  other  materials  c(m- 
taining  little  or  no  carbohydrates  and  which  is  doubtless  often  more 
accurate,  would  not  be  in  jilace  here. 

Kxi)erience  in  this  la])oratory  with  meats  and  other  animal  tissues 
confirms  tlie  observations  of  other  chemists  that  there  is  great  danger 
of  incompletes  ammonification  of  the  nitrogen  in  these  substances  when 
treated  with  sidphuric  acid  ami  other  reagents  as  ordinarily  lecom- 
mended  in  tlieKj(ddahl  process.  Jt  appearsthnl  minierous  albnniinoid 
substances  resist  <le(;omposition,  or  at  any  rate  the  comi)lete  union  of 
nitrogen  and  hydrogen  to  form  ammonia.  With  such  substaiu-es  it  was 
found  necessary  to  continue  the  digestion  for  some  time  after  the  sul- 
plinric  acid  solution  had  Ixniome  coloiless.  'J'he  clearness  of  the  solu- 
tion was  by  no  nu'.ans  an  indication  of  complete  ammonification.  The 
pnxtess  has  frequently  been  found  to  be  incomplete  when  the  digestion 
liad  been  continued  for  an  hour  or  ev<!n  two  hours  after  the  disappear- 
ance of  color.  It  is  safer  to  continue  the  digesti(»n  for  tliree  or  four 
iiours  a,rter  tlie  solution  lisis  become  elecolorized. 


Se*',  II.  S.   I).-])t.   A«r.,  OClicr  of   i:\|..|iiiirlit,  SI:itiuiiH  I'.iil.  'J  I ,  ]..  II. 


26 

Casein. — In  analysis  of  butter  the  casein  was  determined  directly. 
The  butter  was  placed  in  a  Groocli  crucible  and  the  fat  dissolved  out 
with  ether.  The  casein  and  mineral  matters  were  weighed  together  and 
the  casein  burned.  The  loss  in  weight  on  burning  was  taken  as  repre- 
senting the  casein.  The  danger  of  slight  error  here  on  account  of  the 
presence  of  milk  sugar  is  a  subject  which  has  not  been  investigated. 

CARBON   AND    HYDROGEN. 

The  food  materials,  feces,  and  dried  urine  were  burned  with  cupric 
oxid  with  the  aid  of  a  current  of  oxygen,  in  accordance  with  the  usual 
methods.  The  carbon  dioxid  was  absorbed  by  potassium  hydroxid  and 
the  water  by  concentrated  sulphuric  acid.' 

HEATS   OP   COMBUSTION— FUEL   VALUES. 

The  determinations  of  heats  of  combustion  of  food  materials,  feces, 
and  dried  residue  of  urine  were  made  with  the  bomb  calorimeter,  as 
described  in  previous  publications.^  The  apparatus  and  method 
have  been  in  use  in  this  laboratory  for  the  i)ast  three  years,  and  have 
been  found  very  satisfactory. 

COLLECTING,    PI'.ESERVING,    AND   SAJIPLING   OF   FECES   AND    URINE. 

In  the  digestion  experiments  (which  began  before  the  subject  entered 
the  respiration  chamber,  as  explained  beyond)  it  was  necessary  that 
the  feces  of  a  given  diet  should  be  separated  from  those  of  the  diet 
immediately  preceding.  To  effect  a  sharp  separation  the  subject  had  a 
supper  of  bread  and  milk,  at  which  time  he  took  six  or  seven  large  gel- 
atin ciipsules  containing  Iam])black.-'  The  following  morning  the  diet 
decided  upon  for  the  digestion  experiment  was  begun  and  strictly 
adhered  to  throughout  the  whole  exi)eriment.  Tlie  sampling  of  food 
for  analysis  was  also  begun  at  this  first  meal.  On  the  second  or  third 
day  the  milk  feces,  having  a  characteristic  consistency  and  colored  with 
lampblack,  generally  appeared.  When  there  was  no  indication  of 
diarrhea,  the  separation  of  the  residues  from  the  two  different  kinds  of 
food  may  be  considered  reasonably  accurate  inasmuch  as  the  portion 
from  the  meal  of  bread  and  milk  is  easily  distinguished  from  that  of 
the  succeeding  meal.  All  the  feces  following  that  of  the  bread  and 
milk  were  saved.  At  the  end  of  the  experiment  a  supper  of  bread  and 
milk  with  lampblack  was  again  taken,  and  all  the  feces  up  to  the 
point  where  the  milk  residue  apj^eared  were  considered  as  belonging 
to  the  undigested  residues  of  the  diet  under  study.  At  first  the  feces 
of  each  day  during  the  experiment  were  separated,  weighed,  and  in 

iFor  observations  upon  the  sources  of  error  in  the  ordinary  methods  of  analysis  of 
animal  and  vegetable  products,  see  IT.  S.  Dept.  Agr.,  Office  of  Experiment  Stations 
Bill.  21,  pp.  38-52. 

-U.  S.  Dept.  Agr.,  Office  of  Experiment  .Stations  13nl.  21,  pp.  123-126;  Connecticut 
Storrs  Rta.  Rpt.  1894,  i)p.  135-157. 

^Later  experience  has  shown  that  so  nmcli  lampblack  is  unnecessary. 


27 

some  cases  separately  analyzed  also.  This,  however,  proved  unnec- 
essary, as  it  was  found  that  the  composition  with  a  given  diet  remained 
very  nearly  the  same  from  day  to  day. 

The  urine  is  obviously  a  very  important  tsictor  as  regards  the  metabo- 
lism of  nitrogen.  Consequently  its  collection  and  preservation  for 
analysis  require  especial  attention.  Unfortunately  it  was  ])ossiblo  to 
give  only  limited  attention  to  the  subject  during  these  experiments.  It 
is  believed  that  a  more  thorough  investigation  of  the  character  and 
constituents  of  urine  in  respiration  experiments  Mill  prove  of  no  little 
physiological  importance. 

In  these  ex})eriments  the  bladder  was  emptied  every  morning  at  0 
o'clock.  All  the  urine  voided  between  that  hour  and  the  next  morning 
at  the  same  hour  was  taken  as  the  urine  for  that  day.  p]ach  day's 
urine  was  carefully  weighed,  thymol  being  added  as  a  preserving  agent. 

The  total  nitrogen  in  the  urine  was  determined  in  the  fresh  substance 
by  the  Kjeldahl  method. 

For  the  determination  of  carbon  and  hydrogen  the  urine  was  dried 
in  a  partial  vacuum  over  sulpliuric  acid.  It  was  found  by  repeated 
tests  that  drying  urine  by  heat  involves  considerable  loss  of  nitrogen. 
The  importance  of  avoiding  this  loss  led  to  investigations  which  showed 
that  fresh  urine  could  be  dried  in  a  vacuum  over  sulphuric  acid  with- 
ont  material  loss  of  nitrogen.  Accordingly  it  was  assumed  that  there 
would  also  be  extremely'  little  loss  of  carbon  and  hydrogen,  and  the 
substance  thus  dried  was  taken  for  the  determinations  of  these  ele- 
iiicnts.  The  same  method  was  followed,  though  generally  with  a  some- 
what longer  period  of  drying,  to  determine  the  amount  of  water-free 
substance.  The  percentage  of  water  in  this  "  partially  dried  hi  r<(ciio^^ 
urine  was  taken  into  account  in  calculating  the  percentage  of  carbon 
as  determined  by  combustion  with  cupric  oxid. 

ANALYSIS   OF    RESPIRATORY    I'RODUOTS. 

In  ex]>eriments  of  the  class  to  which  those  here  rei)orted  belong  the 
res|)iiatory  produ<-ts  commonly  determined  are  carbon  dioxid,  water, 
and  volatile  organic  compounds. 

CAItnf)X    DIOXII). 

The  determination  of  carbon  dioxid  is  most  essential,  and  is,  of  course, 
always  attempted.  The  experience  of  a  number  of  experimenters  dur- 
ing tlic  past  twenty-five  years  implies  that  the  difficulties  in  the  way  of 
fairly  accurate  results  ar<'  not  insuj>erable.  Tlie  carbon  dioxid  given 
oil"  in  respiration  is  quickly  dilfused  through  the  air  and  readily  con- 
veyed away  by  the  ventilating  cunent,  so  that  the  accurate  measure- 
ment of  that  current  and  dclennination  of  the  jx-rcentage  of  carbon 
<lioxid  Hufliccs  for  the  ordinary  ))Ui|)i)S(',s  of  c^xjierimcnt. 

For  the  al)8orption  of  carbon  dioxiil  soda-lime  lias,  in  onr  cxpciicnce, 
jiroved   tlic  most   siitislactory   reagent.      It   must,   howcAcr,   lia\'e   the 


28 

proper  proportions  of  soda,  lime,  aiul  water  to  fit  it  for  tbe  purpose. 
It  may  be  made  as  follows :  One  kilogram  of  commercial  caustic  soda 
is  treated  with  600  cubic  centimeters  of  water,  forming  a  very  strong 
solution,  or  rather  a  pasty  mass.  To  this  a  kilogram  of  quicklime  is 
added.  The  latter  is  slaked  by  the  water  of  the  soda  solution.  The 
mixture  is  rapidly  stirred.  ISTo  heating  is  necessary.  If  there  are  any 
lumps,  they  are  broken  into  small  pieces,  and  the  soda-lime  thus  made 
is  immediately  put  into  large  bottles  or  fruit  jars  and  tightly  sealed. 

The  presence  of  a  certain  amount  of  moisture  in  the  soda-lime  is 
essential  to  ttie  complete  absorption  of  the  carbon  dioxid.  As  the  soda- 
lime  is  converted  into  the  carbonates  of  sodium  and  calcium  the  mass 
whitens,  and  the  advancement  of  this  change  in  color  from  one  end  of 
the  column  of  soda-lime  to  the  other  is  apparent  as  the  absorption  of 
carbon  dioxid  proceeds.  This  affords  a  very  good  check  on  the  effi- 
ciency of  the  tube.  In  the  preliminary  tests  of  the  method,  as  in  the 
actual  determinations,  two  tubes  were  used  in  series,  and  after  each 
determination  the  second  tube  was  moved  toward  the  incoming  current, 
so  tliat  it  became  the  first  tube,  and  a  fresh  one  was  inserted  to  serve 
as  second  tube.  ISTumerous  experiments  were  made  with  varying  quan- 
tities of  carbon  dioxid  in  the  air  and  with  varying  rates  of  flow  to  see 
if  the  system  would  thoroughly  remove  all  carbon  dioxid.  A  check 
tube  containing  glass  beads  drenched  with  bnrium-hydroxid  solution 
failed  to  indicate  the  slightest  trace  of  carbon  dioxid,  with  150  liters  of 
aspirated  air,  containing  3.5  grams  of  carbon  dioxid,  and  running  at 
the  rate  of  500  cubic  centimeters  per  minute. 

The  value  of  the  soda  lime  as  an  absorbent  for  carbon  dioxid  was 
further  demonstrated  bypassing  a  current  of  air  previously  freed  from 
carbon  dioxid  through  a  flask  in  which  a  known  quantity  of  carbon 
dioxid  was  generated  from  pure  sodium  carbonate  or  calcite.  As  the 
air  with  this  carbon  dioxid  came  from  the  flask  it  was  j)assed  over  sul- 
phuric acid  to  absorb  the  water  and  then  through  two  tubes  containing 
soda-lime,  then  through  a  tube  with  sulphuric  acid  to  catch  the  water 
set  free  from  the  soda-lime,  and  finally  through  a  tube  containing 
barium  hydroxid  solution  to  detect  any  traces  of  carbon  dioxid  which 
might  fail  to  be  absorbed  by  the  soda  lime. 

After  considerable  experience  in  testing  the  methods  by  control 
experiments  of  various  kinds  an  arrangement  of  absorption  tubes  for 
water  and  carbon  dioxid  was  settled  upon,  and  has  skice  proved  very 
satisfactory.  The  order  is :  First,  a  tube  filled  with  pumice  stone  satu- 
rated with  sulphuric  acid  for  the  removal  of  water ;  then  two  tubes 
filled  with  soda  lime  for  the  absorption  of  the  carbon  dioxid ;  and 
finally  a  sulphuric-acid  tube  to  absorb  the  water  removed  from  the 
soda-lime  by  tlie  current  of  air  and  set  free  in  the  formation  of  carbon- 
ates by  the  action  of  the  carbon  dioxid  upon  the  hydroxids. 

It  was  found  important,  however,  to  i)ass  a  current  of  dry  air  through 
the  suli)h uric-acid  tubes  for  three  or  four  hours  before  they  were  used 


29 

iur  the  (letoiiiiiiiations.  since  it  \v;i8  ol)seivecl  tliiit  the  freslily  lilled 
tubes  lost  \veii;ht  when  dry  air  was  lirst  drawn  throujih  them,  the  h)ss 
sonietiuies  anioiuitiiiy  to  20  liiilligraiiis.  A  i)lausibk^,  exphmatioii  of 
this  loss  would  be  found  in  the  assumption  tliat  iuconipletely  oxidized 
eompounds  of  sulpliur  or  introgeu  whieh  were  either  orijiinally  present 
ill  the  acid  or  were  formed  by  its  action  on  the  orj^anic  matter  in  the 
pumice  stone  were  removed  by  the  air  when  lirst  passed  through  the 
tube.  As  the  method  for  avoiding  the  error  i)roved  simple  and  effective, 
we  have  not  taken  the  time  to  in<juire  more  fully  into  the  cause. 

The  determination  of  carbon  dioxid  by  the  above  method  is  (piite 
satisfactory,  as  was  shown  by  numerous  control  exi)eriments.  In  one 
experiment,  for  instance,  which  was  fairly  representative  of  all,  1.(>0JI2 
grams  of  carbon  dioxid  were  delivered  into  the  air  current  and  1.071S 
grams  were  removed  in  the  soda-lime. 

The  weighings  were  all  made  with  a  counterpoise.  To  insure  e(pnil 
moisture  condensation  on  the  tubes  and  counteri)oise,  the  latter  was 
kcjit  in  the  tiay  with  the  U-tubcs,  and  hence  subjected  to  like  conditions 
of  temperature  and  moisture. 


The  accurate  determination  of  water  has  been  found  less  easy.  The 
difficulty  ai)pears  to  rest  not  so  much  in  the  determination  of  moisture 
in  the  current  of  air  as  in  the  getting  of  all  the  moisture  into  the  cur- 
rent. It  is  believed  that  one  chief  trouble  here  n)ay  be  the  adhering  of 
moisture  to  the  surfaces  of  the  walls  and  other  interior  parts  of  the 
apparatus  and  its  absorption  by  the  clothing  of  the  subject  and  the 
furniture  in  the  respiration  chamber.  It  is  evident  that  for  reliable 
results  two  things  are  requisite.  One  is  an  accurate  and  convenient 
method  for  the  determination  of  water  in  a  current  of  air,  the  other  a 
means  for  either  making  sure  that  all  the  water  to  be  determined  is 
contained  in  the  air  current  or  that  the  amount  not  in  that  current 
shall  be  determined  in  some  other  way.  The  water  to  be  determined 
is  the  whole  given  off  from  tlie  body  of  the  subject  in  the  respiration 
chamber,  less  tlie  amount  renioved  in  feces  and  urine.  I'ractically  this 
means  the  water  exhaled  through  the  lungs  and  skin.  I^'or  our  i)resent 
l)uri»ose  it  uiay  be  designated  as  water  of  exhalation  and  taken  as 
including  the  watci-  of  respiration  from  the  lungs  and  that  of  persi)ira- 
tioM  from  the  skin.  Since  the  various  dilhculties  encountered  in  the 
a<*curat«;  determination  of  water  had  not  been  satisfactorily  over(;ome 
when  these  experiments  were  made,  the  results  of  such  determinations 
are  not  reported  in  this  article. 

Tlie  test  of  the  reliability  of  th(;  methods  for  the  determination  of 
the  products  given  off  from  the  body  of  the  person  in  the  respiration 
chamber  must  be  found  in  check  experiments  in  which  known  (pianti- 
ties  of  the  same  i)roducts  will  be  given  off'  in  the  cinunber  and  deter- 
mined in  the  air  current  by  the  methods  used  for  the  actual  experiments. 


30 

Numerous  cbeck  experiments  of  this  kind  preceded  the  experiments 
with  men  reported  beyond.  Tlie  results  indicated  that  the  determina- 
tions of  carbon  dioxid  ^yere  reasonably  accurate.  The  same  was  also 
true  of  the  water  as  iar  as  concerned  the  amounts  actually  contained 
in  the  incoming  and  outgoing  currents  of  air.  It  was  not  certain,  how- 
ever, that  the  moisture  which  was  condensed  upon  the  interior  surface 
of  the  apparatus  (especially  upon  that  part  of  the  apparatus  within 
the  chamber  through  which  the  cold  water  passed  to  carry  away  the 
heat  and  to  which  the  term  heat  absorbers  has  been  applied)  was  the 
same  at  the  beginning  as  at  the  end  of  the  experiment.  The  assump- 
tion that  the  methods  for  the  determination  of  carbon  dioxid  and  water 
in  the  currents  of  air  and  for  the  determinations  of  the  amounts  of 
carbonic  acid  in  the  ai)paratus  were  reasonably  accurate  was  further 
substantiated  by  check  experiments  which  followed  the  present  experi- 
ments with  men. 

The  most  satisfactory  of  these  were  made  by  burning  ethyl  alcohol 
inside  the  chamber.  Tlie  determinations  of  carbonic  acid  differed  by 
less  than  one-half  of  1  per  cent  from  the  theoretical.  In  other  words, 
for  every  100  grams  of  carbon  in  the  alcohol  the  measurements  gave 
from  99.1)  to  100.4  grams.  So  far  as  concerns  the  determination  of  car- 
bonic acid  given  off  inside  the  apparatus,  the  only  difference  between 
these  check  experiments  with  alcohol  and  the  exj)eriments  with  men 
reported  beyond  was  in  the  measurement  of  the  air  current,  which 
could  hardly  have  made  any  very  important  difference  in  the  results. 
It  is  believed,  therefore,  that  the  determination  of  carbon  dioxid  given 
off  by  the  men  in  tlie  experiments  beyond  can  not  be  very  far  from 
correct.^ 


^Before  the  check  experiments  were  made,  arrangemonts  were  perfected  by  wlaieh 
tlie  abs()r2)tion  apparatus  could  be  weighed  by  the  mau  iuside  the  chamber,  so  that 
the  chauges  in  the  amounts  of  water  coudeused  upon  the  surface  of  the  absorbers 
coukl  be  learned.  The  measurements  of  the  volume  of  the  air  were  made  by  the 
improved  apparatus  referred  to  above.     (Sec  p.  20.) 

•Jn  the  check  experiments  with  alcohol  the  determinations  of  water  could  not  be 
made  with  the  same  accuracy  as  in  the  experiments  with  men,  since  in  the  latter  case 
the  absorption  appaiatus  could  be  weighed  by  the  person  inside  the  chamber.  It  is, 
however,  possible  so  to  regulate  the  combustion  of  the  alcohol,  and  hence  the  pro- 
duction of  carbon  dioxid,  water,  and  heat,  that  the,  amounts  produced  during  a  given 
period  at  the  beginning  of  an  experiment  shall  ])e  A^ery  nearly  the  same  as  during  a 
like  period  at  the  end.  Under  these  circumstances  the  amounts  of  water  condensed 
on  the  absorbers  at  the  ends  of  the  two  periods  will  be  approximately  the  same. 
The  control  of  the  amount  of  water  condensed  upon  the  absorbers  is  facilitated  by 
the  ease  Avith  whicii  both  the  temperature  of  the  interior  of  the  apparatus  and  the 
proi)ortion  of  water  in  the  incoming  air  current  may  bo  regulated. 

In  the  check  experiments  made  by  burning  alcohol  m  the  chamber,  pains  were 
takentoiuake  the  conditions  of  (1)  temperature  of  interior  of  apparatus,  (2)  amount 
of  moisture  biought  into  the  apparatus  by  the  incoming  current  of  air,  and  (3)  the 
rate  of  combustion  of  alcohol  approximately  alike  at  the  beginning  and  at  the  end 
of  each  experiment.  These  periods  were  six  hours  or  more  each.  The  experiments 
proper  began  at  the  end  of  the  first  period  and  ended  at  the  close  of  the  second 


31 

VOLATII.K    OIJliAN'lC    COMroiNDS. 

It  has  been  foimd  nece.ssaiy  in  experiments  witli  some  animals,  e.  g., 
oxen,  to  determine  the  qnautities  of  carbon  in  the  hydrocarbons  and 
other  vohitile  orj^anic  couiponnds  given  oflt"  from  tlie  body.  Of  these 
the  most  important  appears  to  be  marsli  gas  prodnced  by  tlie  ferment- 
ative action  of  bacteria  in  the  large  intestine.  Witli  men  the  qnantity 
of  such  compounds  produced  is  apparently  very  small.  They  were  not 
determined  in  the  experiments  here  reported,  although  it  will  doubtless 
be  necessary  to  look  for  such  compounds  and  jterhaps  to  determine 
quantitatively  their  content  of  carbon  and  hydrogen  in  oxi)eriments 
where  the  greatest  accuracy  is  sought. 

THE  EXPERIMENTS. 

The  factors  involved  in  a  complete  metabolism  experiment  and  in 
what  is  commonly  called  a  respiration  experiment  are  fully  explained 
on  page  7.  For  reasons  already  given,  the  account  of  the  respiration 
experiments  here  reported  include  only  the  resnlts  of  measurements  of 
the  income  and  outgo  of  nitrogen  and  carbon.  The  factors  actually 
determined  and  reported  are: 

Income. — Food,  drink,  and  their  content  of  nitrojicn,  carbon,  protein  (N  X  n.25),  fatH 

(etlicr  extract),  carbohydrates  (by  dill'crence),  mineral  matter  (ash). 
Outi/ii. — Respiratory  prodncts— carbon  dioxid  and  its  content  of  carbon. 

Feces — nitrogen,  carbon,  protein  (N  X  6.25),  fats  (ether  extract),  carbohy- 
drates (by  difl'erencc),  mineral  matters  (ash). 
Urine — nitrogen,  carbon. 

As  above  explained,  the  experiments  here  reported  involved  digestion 
experiments.  The  results  of  the  latter  are  included  in  the  descriptions 
which  follow.  The  determination  of  the  digestibility  of  the  several  nutri- 
ents of  the  food  was  made  in  the  usual  way,  by  comparing  the  amounts 
of  protein  fat,  carbohydrates,  and  mineral  matter  in  the  food  and  feces.' 
The  results  of  the  digestion  exi)eriments,  however,  misrepresent  the 
actual  digestion  of  the  food  by  i)ractically  the  amount  of  the  metabolic 
jiroducts  in  the  feces.  The  error,  however,  is  not  large,  and,  so  far  as  the 
resi)iration  exi)eriments  are  coiu^erned,  it  nuiy  be  left  out  of  account 
entirely,  siiu.-e  (he  <piestion  is  the  balance  of  total  a(;tual  income  and 
outgo  of  cheniiital  elements  and  the  metabolic  products  of  the  feces 
are  as  truly  a  part  of  the  outgo  as  the  undigested  residue  of  the  food. 


]teriod,  and  covered  generally  from  twenty-fonr  to  forty-eight  hours.  The  determi- 
nations of  water  in  the  tl)rco  chock  experiments  ranged  from  100.1  to  100.3  ptir  cent 
of  the  thioretlcal  amount.  Improvements  were  also  made  in  the  arrangements  for 
the  determination  of  the  (juantitics  of  hc;it  given  oil'  l)y  tlie  body. 

'See  discnssion  of  this  snliject  in  U.  .S.  iJept.  Agr.,  Olhce  of  lOxiJerimcnt  Stations 
I'.nl.  21,  pp.  56-73. 


32 

THE   DIET. 

In  these  experiments  tlie  effort  was  made  to  have  the  conditions  as 
nearly  normal  as  possible.  To  this  end  it  was  essential  that:  (1)  The 
diet  be  such  as  to  agree  with  tlie  subject,  and  (2)  the  quantities  of 
nntrieuts  be  such  as  to  meet  the  actual  needs  of  the  body  under  the 
conditions  in  which  the  subject  was  placed  during  the  experiment. 

To  facilitate  the  right  choice  of  the  diet,  observations  on  the  ordinary 
diet  of  the  subject  and  a  preliminary  test  of  a  number  of  days  were 
considered  essential.  Accordingly  the  subject  was  allowed  to  select 
his  own  diet  from  a  bill  of  fare  limited  only  by  the  skill  and  appliances 
for  cooking  available.  In  this  way  the  selection  of  food  was  made  such 
as  to  suit  the  palate  and  not  become  so  monotonous  as  to  cause  nausea 
or  any  other  derangement  of  the  processes  of  digestion.  The  subjects 
were  inclined  to  take  more  food  than  was  necessary  for  the  rather 
inactive  life  in  the  respiration  chamber.  It  was  important  to  provide 
that  the  regimen  during  the  experiment  should  be  not  only  such  as 
would  meet  the  actual  needs  as  regards  kinds  and  amounts  of  nutri- 
ents, but  should  also  be  the  same  from  day  to  day. 

The  latter  i^oint  is  especially  necessary.  The  actual  income  for  a 
given  day  or  a  given  number  of  days  is  the  amount  digested  and 
absorbed  during  that  period.  If  the  food  varies  from  day  to  day  there 
is  no  convenient  means  of  learning  to  what  extent  the  proportions  of 
nutrients  digested  vary  with  the  food.  Or,  to  put  it  in  another  way, 
with  varying  diet  the  coefficients  of  digestibility  of  the  several  nutri- 
ents, protein,  fats,  and  carbohydrates,  may  change  and  it  will  be 
impossible  to  tell  how  much  is  digested  from  each  day's  ration  unless  a 
separate  digestion  experiment  is  made  each  day,  which  latter  would 
either  reduce  the  period  of  each  experiment  to  one  day  or  involve  very 
considerable  difficulties  in  the  separation  of  the  feces  for  each  day. 
Furthermore,  only  part  of  the  food  taken  on  a  given  day  is  absorbed 
and  used  in  the  body  on  that  day,  and  it  is  impossible  to  tell  just  when 
the  period  during  which  it  is  being  used  begins  and  ends.  If,  therefore, 
the  diet  varies  from  day  to  day,  there  is  no  way  to  learn  how  the  vari- 
ation affects  the  amounts  actually  absorbed  from  the  alimentary  canal 
and  used  by  the  body  on  the  different  days  during  and  immediately 
following  the  days  when  the  changes  are  made. 

These  considerations  bring  out  one  of  the  chief  sources  of  uncertainty 
in  such  experiments,  namely,  the  impossibility  of  measuring  exactly 
the  amount  of  material  actually  taken  from  the  digestive  tract  and 
brought  into  use  by  the  body  during  a  specitied  period.  It  seemed 
that  the  error  would  be  materially  reduced,  if  not  eliminated,  by  pro- 
viding the  subject  with  a  uniform  diet  for  a  long  period  and  letting  the 
actual  experiment  be  for  a  shorter  period  included  within  this  longer 
period.  This  gives  an  opportunity  to  utilize  the  longer  period  for  a 
digestion  experiment,  the  results  of  whicli  may  be  taken  as  a  measure 
of  the  quantities  of  nutrients  taken  up  and  used  during  the  metabo- 
lism experiment. 


In  accordance  witli  these  considerations,  the  subject  commenced  a 
specitied  regimen  some  days  in  advance  of  each  experiment.  To  adjust 
the  quantities  of  food  materials,  so  as  to  secure  the  proper  proportions 
of  nutrients,  estimates  were  made  in  advance  by  use  of  the  figures  for 
composition  of  American  materials/  The  exact  amounts  of  protein, 
fats,  and  carbohj'drates  were,  of  course,  not  learned  until  the  analyses 
were  made.  Fortunately,  the  actual  composition  as  thus  found  was 
very  close  to  the  atlvance  estimates  in  every  case. 

"Meals  were  eaten  three  times  daily  at  regular  hours,  thus  conforming 
as  far  as  possible  to  ordinary  custom.  Drinking  water  was  allowed  at 
all  times,  the  weight  used  and  the  temperature,  however,  being  care- 
fully noted.  The  freedom  allowed  in  the  selection  of  diet  added,  it  is 
believed,  materially  to  the  success  of  the  experiment,  although  the 
number  of  different  materials  ma<le  the  analyses  quite  laborious. 

Although  the  diet  in  each  experiment  was  comparatively  simple,  a 
considerable  number  of  food  materials  were  analyzed.  The  composi- 
tion of  the  various  foods  is  given  in  the  following  table: 

Tabi.k  1. — Compoxition  of  food  materials  used  in  the  experiments. 


2690 

2tin9 

2704 
2715 
2t;!l5 
2fi'.l8 
2705 
42:!8 
42:!9 
4248 
4249 
4228 
42:i7 
4227 
424U 
4247 
4250 
2697 
2701 
269:j 
27o:{ 

2724 
2727 
2726 
272:i 
2728 
2694 
2700 
2708 
2725 
27119 
2707 

27  ri 


BP«?f.fripd 1 

do 2 

do 3 

do 4 

KgfTs,  boiled 1 

.....do 2 

do 3 

Butttr 1 

do 2 

do 3 

do 4 

Clu-esoa 1 

doa 2 

Milk 1 

do 2 

do 3 

do 4 

CrackerM,  milk 1 

do 2 

JJrend.rye >    1 

do 2 

IJrcad,  white 3 

do I     4 

lircad.lirown j     4 

4 
4 
1 
2 
3 
4 
(fc) 


Oatinial 

lii^aiiH, dri<  d. ... 

I'otatoi  H,  iMiilud 

do 

do 

do 

Ai()deH 

IVaclies I    3 

•Sugar (c) 


Per  ct. 

4.64 

4.85 

4.73 

5.48 

2.07 

1.99 

2.41 

.14 

.16 

.14 

.18 

4.29 

4.07 

.58 

.54 

.53 

.53 

1.78 

1.6/ 

1.47 

1.43 

1.31 

1.48 

.93 

2.75 

1.10 

.35 

.30 

.37 

.40 

.04 

.09 


Per  ct. 

21.24 

23.00 

20.26 

23.18 

14.45 

14.95 

15.43 

64.64 

66.40 

67.07 

66.85 

33.  43 

35.80 

7.27 

6.79 

0.17 

0.01 

44.00 

44.01 

25.  85 

25.  63 

25.  83 

27.  82 

22.27 

41.15 

11.37 

8.00 

9.54 

9.08 

9.77 

5.  r>9 

4.87 

42.06 


Per  ct. 
3.35 
3.43 
?.91 
3.46 
2.25 
2.42 
2.55 
9.69 
9.69 
9.78 
9.89 
4.88 
5.20 
.94 
1.00 
1.02 
1.00 
6.54 
7.08 
2.37 
3.97 
3.77 
3.89 
3.13 
5.83 
1.57 
1.27 
1.36 
1.48 
1.41 
.78 
.57 
6.45 


Per  ct. 

58.9 

56.4 

60.3 

53.5 

73.3 

72.4 

69.2 

9.2 

8.9 

8.1 

8.9 

44.1 

39.7 

85.9 

85.9 

85.9 

86.2 

5.7 

5.5 

39.0 

40.4 

39.1 

35.6 

47.2 

8.9 

72.8 

80.8 

76.8 

74.8 

75.8 

86.7 

89.3 


oX 


Per  ct. 

29.0 

30.3 

29.5 

34.2 

12.9 

12.4 

15.1 

.9 

1.0 

.9 

1.1 

26.8 

25.4 

3.6 

3.4 

3.3 

3.3 

11.1 

10.4 

9.2 

9.0 

8.2 

9.2 

5.8 

17.2 

6.9 

2.2 

2.3 

2.3 

2.5 

.2 

.6 


Per  ct. 

9.8 

11.1 

8.1 

10.4 

11.3 

13.0 

13.2 

80.3 

85.4 

88.4 

86.9 

24.  5 

27.0 

4.2 

4.5 

4.5 

4.2 

12.3 

12.2 

.2 

.2 

1.3 

1.4 

1.2 

7.0 

.4 

.1 

.  1 

.1 

.1 

.2 

.1 


o  ^ 


Per  ct. 

1.0 

.7 


1.2 

4.0 

5.5 

5.5 

5.5 

5.6 

09.6 

69.  3 

50.3 

49.0 

50.0 

52.8 

43.6 

65.2 

18.0 

16.2 

19.8 

21.7 

20.6 

12.7 

9.7 

100.0 


Per  ct. 
1.3 
1.5 
2.0 
2.0 
1.0 
1.0 

1.1 

3.6 

4.7 

2.7 

3.1 

3.4 

3.9 

.8 

.7 

.8 

.7 

1.3 

2.6 

1.3 

1.4 

.8 

1.0 

2.2 

1.7 

1.9 

.7 

I.O 

1.1 

1.0 

.2 

.3 


■la 


p^' 


Calories. 
2.494 
2.758 
2.424 
2.904 

1.  897 
2.043 
2. 123 
8.  122 
8.184 
8. 4:t5 
8.  169 
3.800 
4.  219 

.836 

.822 

.807 

.798 

4.677 

4.679 

2.681 

2. 007 

2.735 

2.  892 
2.  305 
4.409 
1.  179 

.787 
.905 

1.032 
.  989 
.547 
.470 

3.987 


aTliem;  two  Hanipl<;M  of  cIii'<>hi-  Ix-caiiio  p.irtialiy  de(;oin|)osfd  beforo  tlio  doltMininatioii.s  of  carbon, 
hydroKori,  and  lii^atH  of  combMHtioii  coiibl  bf!  iiiad'o.  Tlic  figures  for  faclnrH  iiiiiiicrl  liavi-  \mfu  caliMi- 
laU-d  from  \\n:  jMT<-i-nlaj;<'H  of  pro! ••in,  fatH.  and  carlioliydrati-H  by  im(!of  I  be  indors  0.5:i,  0.765,  and  0.41, 
r^MiHclivcly,  lor  tlM-conlcrit  of  carbon,  and  0.07,  0.12.  and  0  00,  rcs|>c<;tivi'ly,  for  Ibo  liydro^'on  contc^nt; 
till-  b<at»  of  conibiiHtion  witc  calciilutcd  from  tiio  valucH  previoiiHly  found  in  two  Biniilar  aan)i)loH. 

'/KxpcrinifiilH  Noh.  3  and  4. 

cKx  peri  Mien  U  Noh.  1,  2,  3,  and  4. 


'  11.  .S.  Dcjtt.  A^r.,  Odiiu-  (iC  Expcritnoiit  Statiou.4  liul.  28. 
2771— No.  44 3 


34 

DAILY  ROUTINE. 

The  digestion  experiment  which  was  made  with  each  respiration 
experiment  commenced  two  or  three  days  before  the  latter,  but  both 
ended  at  the  same  time.  On  the  second  or  third  day  of  the  digestion 
experiment  the  subject  entered  the  respiration  chamber,  but,  in  order 
to  insure  normal  conditions,  the  respiration  experiment  did  not  begin 
until  six  hours  after  he  had  entered.  This  allowed  the  subject  an 
opportunity  for  arranging  his  furniture,  the  hygrometer,  thermometer, 
and  other  apparatus  in  the  room,  and  permitted  the  establishment  of 
the  needed  equilibrium  of  temperature  and  moisture  content  in  the 
chamber  preparatory  to  the  respiration  experiment  itself. 

The  food  and  drink  were  passed  in  and  the  solid  and  liquid  excreta 
were  removed  through  the  food  aperture  in  the  side  of  the  apparatus. 
A  comfortable  temperature  was  maintained  within  the  room  by  means 
of  a  current  of  cold  water,  which  passed  through  the  pipes  of  the  heat 
absorbers  inside  the  chamber  and  thus  brought  away  the  heat  radiated 
from  the  man's  body.  The  temperature  which  best  suited  the  feelings 
of  the  subject,  generally  not  far  from  20°  C,  was  maintained  through- 
out the  whole  of  each  experiment,  except  during  one  period  of  the  last 
exi)eriment,  when  the  subject  was  engaged  in  hard  muscular  work.  In 
this  case  a  very  large  amount  of  heat  was  given  off' from  the  body,  and 
the  current  of  cold  water  passing  through  the  absorbers  did  not  suffice 
to  prevent  the  temperature  from  rising  at  times  to  23°  or  24°.  As  this 
high  temperature  was  maintained  for  only  a  few  hours  at  a  time,  it  is 
clearly  an  exception  to  the  rule. 

The  occupants  of  the  chamber  passed  the  time  in  such  ways  as  were 
in  general  most  agreeable  under  the  circumstances.  They  observed 
regular  hours  of  eating  and  sleeping.  There  was,  of  course,  almost  no 
opportunity  for  exercise.  In  the  last  experiment,  however,  a  si^ecial 
arrangement  was  made  for  vigorous  muscular  labor  in  lifting  and 
lowering  a  weight  suspended  from  a  pulley.  This  arrangement  will 
be  described  in  connection  with  the  other  details  of  the  exi:)eriment. 
Abundant  oj)portunity  was  given  for  reading,  considerable  conversa- 
tion was  held  between  the  occupant  and  the  men  who  did  the  work  out- 
side, and  the  monotony  was  also  relieved  from  time  to  time  by  visitors. 

Since  the  experiments  went  on  day  and  night,  relays  of  the  force  for 
day  and  night  work  were,  of  course,  necessary.  During  the  day  a 
force  of  five  or  six  persons  was  generally  employed.  During  the  night, 
when  the  occupant  of  the  chamber  was  asleep,  the  force  was  reduced 
to  three. 

A  brief  description  of  the  routine  of  one  day  will  perhaps  help  to  a 
better  understanding  of  the  way  in  which  the  experiment  was  carried 
out.  The  night  force  of  operators  was  relieved  at  7  o'clock  a.  m.  At 
that  time  the  subject  was  awake  and  ready  for  breakfast.  The  assist- 
ant, who  had  charge  of  the  preparation  and  cooking  of  the  food,  pre- 
pared the  breakfast  5  the  chemist  of  the  night  force  changed  the  system 


I 


35 

of  U  tubes  for  analysis  of  the  air.  The  day  chemist  proceeded  to  start 
the  i)assage  of  the  air  through  the  fresh  system  of  tubes,  and  then 
weighed  the  system  which  had  just  beeu  removed;  the  readings  of  the 
meter  by  which  the  ventilating  current  of  air  was  measured,  and  of 
temperature,  barometric  j^ressure,  etc.,  were  made.  The  subject,  hav- 
ing emptied  the  bladder  at  G  a.  m.,  passed  out  the  liquid,  and  at  the 
same  time  the  solid  excreta.  The  readings  of  the  hygrometer  and 
thermometer  inside  the  apparatus  were  taken  by  the  subject  on  rising, 
and  the  observations  were  repeated  once  in  two  hours  throughout 
the  day.  Naturally,  the  inquiry  regarding  the  subject's  physical  con- 
dition, and  any  changes  needed,  received  early  attention  in  the  morning. 

Breakfast  was  ordinarily  served  at  about  half  past  7  o'clock,  dinner  at 
about  half  past  12  o'clock,  and  .supper  at  6  o'clock.  Drinking  water 
was  given  Mhenever  desired,  its  weight  and  temjierature  being  noted. 

The  freezing  apparatus  required  repacking  with  ice  and  salt  about 
once  in  two  hours  during  the  day  and  night;  the  rate  of  flow  of  water 
through  the  aspirators  by  which  the  samples  of  air  for  analysis  were 
drawn  was  regulated  every  half  hour.  The  temperature  of  the  air  of 
the  meter  was  recorded  hourly.  The  freezers  through  which  the  outgoing 
air  passed  were  changed  once  in  twelve  hours,  and  the  water  condensed 
in  them  was  weighed.  The  absorption  tubes  for  the  water  and  carbon 
dioxid  of  the  air  sami)les  were  changed  once  in  six  hours,  at  which  time 
the  temperature  of  the  aspirators,  the  temperature  of  the  meter,  and 
the  readings  of  the  meter  and  of  the  air-pump  register  were  recorded. 

Concurrently  with  all  of  these  operations,  the  analytical  work  was 
carried  on  and  completed  as  rai)idly  as  possible. 

COMPUTATION   OF   RESULTS. 
XITROGEN   BALANCE. 

Kitrof/cn  in  urine. — In  the  estimate  of  nitrogen  balance  the  measure 
of  the  nitrogen  metabolized  in  the  body  during  a  given  period  is  sought 
in  the  nitrogen  of  the  urine  for  a  period  of  equal  length.  The  i)eriod 
is  commonly  a  day  of  twenty-four  hours.  The  jieriod  for  collecting  the 
urine,  however,  can  not  be  coincident  with  that  for  whi(;h  the  nitrogen 
metaljolism  is  to  be  measured,  since  some  time  isrecjuired  for  the  metab- 
olize<l  nitrogen  to  be  conveyed  to  the  kidneys,  passed  into  the  bladder, 
and  afterwards  excreted  in  the  urine.  The  twenty-four-hour  period  for 
iollccting  tlu;  urine  must  therefore  begin  and  end  later  tiian  the  cor 
i«*sp()ii(iing  nitrogen-nuitabolism  period  of  twenty-four  hours.  This 
interval,  during  which  the  excretion  of  nitrogen  lags  behind  the  metab- 
olism, may  for  convenience  be  termed  the  "nitrogen  lag."  Unfortu- 
nately there  ai«;  few  data  for  judging  accurately  as  to  the  length  of  this 
interval  of  lag.  Indeed  one  of  the  most  dillicult  problems  in  experi- 
ments of  this  class  is  to  determine  the  actual  source  of  the  nitrogen 
excreted  in  the  urine — that  is,  to  determine  whether  the  identical  nitro- 
gen of  the  food  is  excreted   in  the  urine  after  a  short  interval,  or 


36 

whefher  the  nitrogen  becomes  part  of  the  body  tissue  and  an  equiva- 
lent amount  (derived  from  the  body)  is  excreted. 

Kolpakcha^  has  recently  made  some  interesting  experiments  with 
dogs  which  bear  on  this  problem.  He  compared  the  ratio  of  phospho- 
rus and  nitrogen  and  sulphur  and  nitrogen  in  the  food  and  urine  under 
various  dietary  conditions,  and  also  when  no  food  was  consumed.  These 
ratios  were  found  to  vary  under  the  different  dietary  conditions.  The 
conclusion  was  reached  that  when  the  food  supply  was  adequate  very 
little  nitrogenous  tissue  was  broken  down,  i.  e.,  the  nitrogen  excreted 
actually  came  from  the  food.  An  excess  of  protein  eaten  over  the 
amount  required  was  stored  up  inside  the  cells  of  the  protein  tissue  of 
the  body,  but  was  not  immediately  made  a  part  of  the  actual  tissue. 
It  was  simply  reserve  material.  After  a  few  days  of  fasting,  this 
reserve  was  exhausted  and  the  body  was  then  compelled  to  draw  on  its 
own  protein.  Since  the  above-mentioned  period  is  short,  the  conclusion 
seems  warranted  that  in  the  case  of  dogs  the  actual  nitrogen  consumed 
in  the  food  is  soon  excreted  under  ordinary  conditions. 

In  the  present  experiments  a  lag  of  six  hours  was  assumed  in  one  case 
and  a  lag  of  twelve  hours  in  another.  The  fluctuations  in  the  daily 
excretion  of  nitrogen  in  the  experiments  herewith  reported  when  the 
diet  and  other  conditions  were  reasonably  uniform  indicate,  however, 
that  it  is  impossible  to  make  any  accurate  estimate  of  this  interval  of 
lag.  These  fluctuations  are  shown  in  the  statistics  of  the  nitrogen 
excretion  in  Tables  5,  12, 19,  and  26. 

It  is  a  familiar  fact  that  some  materials  may  be  excreted  by  the  urine 
within  a  very  short  time  after  they  have  been  taken  in  the  food.  Thus 
it  is  a  common  observation  that  the  peculiar  odor  of  urine  which  comes 
from  asparagus  may  be  observed  within  an  hour  after  eating  the  latter. 
In  several  rough  tests  made  in  this  laboratory  very  small  quantities 
of  i)otassium  iodid  were  administered  to  a  person,  and  a  perceptible  test 
for  iodin  was  obtained  in  the  urine  within  half  an  hour  after  taking 
the  salt. 

Such  observations  as  these,  however,  do  not  give  exact  indications 
of  the  rapidity  of  secretion  and  excretion  of  metabolized  nitrogen. 
Thus  it  was  found,  in  experiment  No.  4  (p.  51),  where  the  metabolism 
of  nitrogen  was  materially  increased  by  severe  muscular  work  during 
a  period  of  three  days,  that  the  increase  of  nitrogen  in  the  urine  appar- 
ently lagged  a  day  behind  the  period  of  increased  muscular  exercise, 
and  after  the  muscular  work  stopped  there  was  a  similar  lag  in  the 
return  of  the  nitrogen  of  the  urine  to  the  i)revious  level  of  muscular 
rest.  In  this  case,  however,  the  data  do  not  exactly  define  the  time  of 
rise  aijd  fall  of  nitrogen  secretion  or  excretion.  If  the  urine  had  been 
collected  and  its  nitrogen  determined  every  six  hours  instead  of  mixing 
the  amount  collected  for  twenty-four  hours  together  and  making  but  a 

iPhysiologicheskii  Sbornik.,  1  (18S8),p.56. 


37 

single  analysis,  as  was  actually  done,  the  results  might  have  given  a 
closer  indication  of  the  relation  between  the  times  of  increased  and 
decreased  metabolism  and  those  of  increased  and  decreased  excretion 
of  nitrogeu. 

The  experiments  here  reported  were  divided  into  experimental  days 
of  twenty-four  hours.  These  experimental  days  were  not  calendar 
days  beginning  at  un<lnight,  but  were  made  to  begin  at  such  houis  as 
were  most  convenient.  In  experiment  No.  4  the  nitrogen  .was  col- 
lected and  examined  during  twenty-four  hour  ])eriods,  each  beginning 
and  ending  six  hours  after  the  corresi)()nding  ex])erimental  day.  The 
arrangements  and  calculations  for  experiments  1  and  ii  were  somewhat 
dift'erent  from  those  for  experiments  3  and  4,  as  explained  on  page  49. 

The  principal  factors  involved  in  the  computation  of  the  nitrogen 
balance  may  1)6  stated  as  follows : 

d)  yUrogen  of  food. — This  represents  tlic  gross  income. 

(2)  Xitrogeii  of  feres. 

i'.i)  NUroi/dt  of  «?•(■««. — This  is  mainly  the  nitrogen  of  compounds  from  the  food 
and  hody  tissue  which  have  not  hccu  completely  oxidized,  the  most  important  hcing 
urea. 

Nos.  '2  and  3  together  make  up  the  gross  outgo  of  nitrogen. 

(4)  Nitrogen  of  food  digiiiUd  (Did  ahsorhed  and  thus  made  available  for  use  in  thi' 
body.  This  is  the  total  nitrogen  less  th.it  of  the  feces.  Its  amount  is  found  hy  sub- 
tracting Xo.  2  from  No.  1.  It  may  be  designated  as  "  tot.'il  available"  nitrogen,  i.  e., 
the  total  available  for  metabolism. 

(5)  Nitrogen  gained  or  lout  hij  the  hody. — If  more  nitrogen  is  taken  into  the  body 
than  is  given  off — in  other  words,  if  No.  ]  is  greater  than  the  sum  of  Nos.  2  and  .%  or, 
what  is  the  same  thing,  if  No.  4  is  greater  than  No.  3 — the  difference  will  1)e  the 
amount  the  body  has  gained.  If,  on  the  other  hand,  the  body  has  given  off  more 
nitrogen  than  it  has  received,  the  difference.  No.  3  less  No.  4,  is  the,  amount  lost.  It 
is  customary  to  multiply  the  amount  gained  or  lost  by  6.25  and  to  assume  that  the 
product  represents  the  gain  or  loss  of  i>rotein. 

CAllBON    IJALANCE. 

In  like  manner  the  principal  data  involved  in  the  computation  of  the 
carbon  balance  may  be  succinctly  groui)ed  as  follows: 

(1)  Carbon  of  food. — This  is  the  gross  income. 

(2)  Carbon  of  feces. 
( '.i )   Car  bo  n  of  urin  e. 

(i)  Carbon  of  carbon  dioxid  exhaled. 

NoH.  2,  3,  and  4  together  make  u]i  the  gross  outgo. 

(.">)  Carbon  of  fooil  digested  and  absorbed  and  thus  made  avail.able  for  metabolism. 
It  is  found  by  subtracting  No.  2  from  No.  1,  and  may  be  designated  as  "  total  avail- 
able" «;arlion,  i.  e.,  t<»tal  available  for  lufitaliolism.  The  (iarbon  of  the  metabolic 
jtroductH  of  the  feces  is  here  treated  as  if  it  were  a  i)art  of  the  undigested  residue 
of  the  food. 

(Ct)  Carbon  acluallg  utilized. — This  is  the  carbon  absorbed  less  that  excreted  by 
the  kirlneys  in  the  form  of  urea  and  other  jtroducts  of  incomplete  oxidation  of 
organic  compoiiiidH.  It  is  found  by  subtracting  No.  3  from  No.  5,  and  may  be  desig- 
natid  as  "net  available"  carl)on,  I.  e.,  tiie  total  amount availabli'  (or  building  tissue 
or  yielding  euergy. 


38 

(7)  Carhon  gained  or  lost  iy  the  hody.—U  No.  1  is  greater  than  the  snm  of  Nos.  2,  3, 
and  4,  or,  what  is  the  same  thing,  if  No.  5  exceeds  the  sum  of  Nos.  3  and  4,  the  dif- 
ference Avill  represent  the  gain  in  carhon.  If,  on  the  other  hand,  the  hody  has  lost 
carhon  the  amount  will  he  found  hy  suhtracting  No.  5  from  the  sum  of  Nos.  3  and  4. 

GAIN   AND   LOSS    OF   TROTEIN   AND   FAT. 

The  metliod  usually  followed  in  these  computations  is  the  one  origi- 
nally proposed  by  Pettenkofer  and  Voit  and  used  by  them  and  other 
experimenters.  It  assumes  that  the  nitrogen,  carbon,  and  hydrogen 
gained  or  lost  by  the  body  belongs  to  either  protein  compounds,  fats, 
or  carbohydrates,  and  that  these  have  definite  proportions  of  nitrogen, 
carbon,  and  hydrogen.  On  this  basis  the  quantities  of  these  three 
elements  gained  or  lost  would  serve  as  data  for  computation  ot  the  gain 
or  loss  of  each  one  of  the  compounds. 

Of  course  these  assumptions  are  not  entirely  accurate,  but  they  are 
enough  so  for  our  present  purpose.     Even  if  they  were  accurate  it 
would  be  impossible  to  tell  exactly  how  much  of  either  class  of  com- 
pounds was  actually  metabolized  and  actually  stored  in  the  body  or 
resolved  into  its  constituents  and  given  off'  from  the  body.    It  would 
only  be  possible  to  estimate  the  difference  between  the  total  amount 
of  each  substance  which  was  stored  and  the  total  amount  which  was 
broken  up  and  burned.      As  regards  the  protein  stored  or  lost,  it  is 
impossible  to  tell  how  much  belongs  to  either  cell  tissue  or  cell  contents, 
or  how  much  has  simply  formed  a  part  of  the  blood  or  other  fluids. 
The  case  is  entirely  analogous  with  the  fats  and  carbohydrates.    But 
it  seems  fair  to  assume  that  the  increase  or  decrease  of  nitrogenous 
material  will  be  mainly  that  of  the  proteid  compounds,  which  belong 
IDroperly  to  connective  and  contractive  tissue,  and  inasmuch  as  the 
proportion  of  nitrogen  in  all  these  is  approximately  10  per  cent,  the 
quantity  of  protein  gained  or  lost  during  the  experiment  corresponds 
to  very  nearly  6.25  times  that  amount  of  nitrogen.     With  the  nitrogen 
of  protein  is  a  certain  nearly  constant  amount  of  carbon.     It  is  easy, 
therefore,  to  compute  the  amount  of  the  latter  element  Avhicli  is  either 
stored  by  the  body  or  lost  from  the  body  in  protein.     The  algebraic 
difference  between  the  protein  carbon  gained  or  lost  and  the  total  car- 
bon gained  or  lost  represents  the  carbon  gained  or  lost  in  carbohydrates 
and  fats.     If  we  had  the  balance  of  hydrogen,  or,  better,  the  balance 
of  hydrogen  and  oxygen,  and  could  assume  definite  quantities  of  car- 
bon, hydrogen,  and  oxygen  for  the  carbohydrates  and  fats,  it  would  be 
easy  to  calculate  the  amounts  of  these  and  of  water  actually  gained  or 
lost.    It  is,  however,  common  to  assume  that  the  quantity  of  carbohy- 
drates in  the  body,  which  is  very  small,  is  not  materially  changed,  and 
that  consequently  the  carbon  gained  or  lost  outside  of  that  in  the  pro- 
tein belongs  to  fat.    Accordingly  the  gam  or  loss  of  carbon  outside 
that  belonging  to  the  protein  gained  or  lost  is  taken  as  representing 
the  quantity  of  fat  gained  or  lost.     In  calculations  here  used  it  is 
assumed  that  the  protein  contains  IG  per  cent  of  nitrogen  and  53  per 
cent  of  carbon,  and  that  the  fat  contains  76.5  per  cent  of  carbon. 


39 

The  method  of  conipatation  may  be  expressed  algebraically  as  follows : 
Let  the  amount  of  gain  or  loss  of  nitrogen  be  represented  by  i  K  and 
the  amount  of  gain  or  loss  of  carbon  by  iO.    Then: 
±  N  X  0.25  =  protein  gained  or  lost  =  i  P 
zt  P  X  0.53  =  carbon  gained  or  lost  in  protein  =  C  (protein) 
=t  C  ^  C  (protein)  =:  carbon  stored  or  lost  as  fat  =  C  (fat) 
±  C  (fat)  -^  0.7(J5  =  fat  gained  or  lost. 


The  potential  energy  of  the  ingredients  of  food  is  commonly  estimated 
by  the  use  of  the  factors  proposed  by  llubiier,'  which  assign  4.1  calories 
to  each  gram  of  protein  or  carbohydrates  and  9.3  calories  to  each  gram 
of  fat.  This  figure  for  protein,  however,  represents  a  net  fuel  value, 
and  is  obtained  by  subtracting  from  the  total  fuel  value  of  protein, 
taken  as  o.~)  calories  per  gram,  the  value  for  the  nitrogenous  comi^ounds, 
including  urea,  not  completely  oxidized. 

In  the  experiments  here  described  the  heats  of  combustion  of  the 
food  materials,  feces,  and  dry  matter  of  urine  Averc  determined  directly 
by  the  use  of  the  bomb  calorimeter,  as  above  stated.  The  figures  given 
in  the  tables,  therefore,  represent  the  results  of  these  determinations 
rather  than  estimates  made  by  the  use  of  factors.  In  the  computations 
of  energy  of  the  protein  and  fat  gained  or  lost  from  the  body,  however, 
it  is,  of  course,  necessary  to  use  factors.  For  protein  gained  or  lost 
tlie  factor  5.5  was  employed.  For  the  fat  gained  or  lost  the  factor  9.4 
was  used  as  representing  tlie  heat  of  combustion  of  liuman  fat  per  gram. 

The  principal  data  involved  in  these  comi)utations  may  be  classified 
as  was  done  with  those  of  nitrogen  and  carbon  above. 

(1)  Total  energy  of  nutrients  of  food,  or  total  energy  of  income.  'I'liis  is  rei)resente(l 
by  the  heats  of  comhustioii  of  the  food  materials. 

(2)  Enn-gy  in  feces,  actual  heats  of  comljiistion. 

(3)  Kiiergy  in  urine,  boats  of  comlnistroii  of  dry  matter. 

(4)  '/'olal  energy  in  food  digested  and  alimrhed. — This  is  usually  found  by  subtracting 
No.  2  from  No.  1,  and  may  be  de8ignatc<l  as  total  urailahle  energy.  This  valu<'  obtained 
]iy  difference,  liowevcr,  does  not  exactly  re])resent  the  fuel  value  realized  from  tlie 
digeste<l  food,  for  the  reason  that  there  is  always  a  portion  of  digested  food  which 
IS  not  com])letely  oxidized — namely,  the  organic  matter,  mainly  nitrogenous,  which 
is  isecreti-d  by  the  kidneys  and  excrcited  in  the  urine.  Assuming  the  organism  to  bo 
in  nitrogftu  equilibrium,  the  heat  of  combustion  of  this  partially  oxidiztxl  material 
may  be  assumed  to  be  that  of  tli(!  water-free  substance  of  the  urine.  For  the  diges- 
tion experiment,  in  wliich  the  gain  and  loss  of  body  material  are  left  out  of  account, 
it  is  most  convenient  to  estiimite  tins  find  value  of  this  i)artly  oxidized  nilrogenous 
material  and  8ul>tract  it  from  th<^  total  heat  of  combustion  of  the  digeste<l  food. 
For  this  ]iurpoHe  it  is  assumed  that  the  whole  will  be  in  the  form  of  ure.a,  and  that 
the  amount  of  the  latter  will  corresponil  to  the  amount  of  digested  nitrogen. 

(.5)  Set  energy  of  food  digmled  and  ahuorbed. — If  jirotein  is  iieitluir  gained  nor  lost, 
the  net  energy  is  fouml  liy  subtracting  No.  3  from  No.  4.  If  protein  is  stored,  No.  !5  is 
too  small  by  the  value  of  the  urea  and  kindred  comjiounds  cornisponding  to  the 
nitrogen  in  the  prot<-in  stored.     If  protein  is  lost,  No.  3  is  too  large  ))y  the  energy  of 

'  ZtHciir.  Miol.,  21  (IS85),  p.  250. 


40 

the  urea  which  comes  from  the  protein  lost.  The  fuel  value  of  urea  correspondiug 
to  1  gram  of  i^rotein  is  0.87  calories.' 

If,  then,  the  protein  stored  or  lost  is  multiplied  by  0.87  and  the  product  added  to 
No.  3  Avheu  protein  is  stored  and  subtracted  from  it  when  lost,  the  energy  of  the 
urine  correspondiug  to  the  protein  digested  is  obtained.  In  other  words,  the  net 
energy  of  the  food  digested  is  No.  4 -(No.  3  J- 0.87  X  protein  gained  or  lost). 

It  is  extremely  probable  that  further  consideration  of  the  subject,  together  with 
investigations  now  contemplated,  may  lead  to  more  or  less  change  in  the  details  of 
the  method  here  employed  for  the  estimation  of  energy  of  the  compounds  in  ques- 
tion, including  especially  the  nitrogenous  compounds.  This  method  will,  however, 
suffice  for  the  present  use,  which  is  only  tentative. '^ 

(6)  Energy  liberated  as  heat  or  manifested  as  external  muscular  work. — If  a  balance  of 
energy  is  to  be  made,  another  factor  must  be  talten  into  account,  namely,  the  heat 
radiated  from  the  body,  and  that  equivalent  to  the  external  muscular  work  per- 
formed. Though  this  was  measured  in  the  present  experiment,  for.  the  reason 
already  stated,  the  results  are  Avithheld,  and  the  balance  of  income  and  outgo  of 
energy  is  not  given. 

RESPIRATION  EXPERIMENT  No.  1  (DIGESTION  EXPERIMENT  No.  ]1). 

The  subject  in  this  experiment  was  a  Swede  29  years  of  age  who 
acted  as  Laboratory  janitor  and  was  accustomed  to  a  moderate  amount 
of  muscular  work.  He  would  be  called  a  hearty  eater.  During  the 
X)rogress  of  the  experiments  he  read  a  little  for  diversion,  but  the 
larger  part  of  the  time  was  as  free  from  mental  and  physical  activities 
as  practicable.  While  he  was  entirely  willing  to  do  everything  that 
was  required  of  him,  it  became  evident  that  he  did  not  find  the  sojourn 
in  the  chamber  entirely  agreeable.  Toward  the  end  of  the  second 
experiment  he  became  somewhat  ill,  but  the  circumstances  were  such 
that  it  could  hardly  be  attributed  to  impure  air  or  any  other  abnormal 
condition ;  indeed,  there  seemed  to  be  good  ground  to  believe  that  the 
slight  illness  was  caused  by  nervousness  due  to  the  sojourn  in  the  res- 
l^iration  chamber  and  an  undefined  and  unfounded  fear  that  some 
trouble  might  result. 

The  diet  was  comparatively  simple.  It  was  of  his  own  selection 
and  was  made  up  of  such  foods  as  he  would  have  eaten  under  ordinary 
conditions.    Three  meals  a  day  were  eaten.    Water  was  consumed  ad 

lUrea,  CON3H4,  contains  46.67  per  cent  of  nitrogen;  consequently  NX  2. 143= urea. 
From  the  values  obtained  by  Berthelot,  Stohmanu,  and  others,  the  fuel  value  of  urea 
may  be  taken  as  2.53  calories  per  gram.  Assuming  that  all  of  the  digested  protein 
is  consumed  in  the  body  to  urea,  we  can  find  the  theoretical  value  of  the  urea  cor- 
responding to  1  gram  of  protein  as  follows:  Weight  of  protein  — 6.25  =  weight  of 
nitrogen.  Weight  of  N  X  2.143:=  weight  of  urea.  Weight  of  urea  x  2.53^heat  of 
combustion  of  urea.     Or  the  heat  of  combustion  of  the  urea  corresponding  to  1  gram 

of  protein  is  -^ — (C^K^ — =0.87  calorics.  The  subject  of  metabolism  of  energy  is  dis- 
cussed in  U.  S.  Dept.  Agr.,  Office  of  Experiment  Stations  Bui.  21,  p.  113. 

2  Eubner,  Ztschr.  Biol.,  21  (1885),  p.  337.  The  results  of  the  present  experiments, 
both  those  given  beyond  and  others  still  unijublished,  agree  entirely  with  Kubner's 
in  showing  that  the  heat  of  combustion  of  the  dry  matter  in  the  urine  is  much 
larger  than  that  of  the  urea,  which  would  correspond  to  the  nitrogen  in  the  urine. 


41 

libitum.    The  foods  coiisiiined  at  each  meal  are  shown  in  the  following 
table : 

Table  2. — Daily  mvuit,  respiration  experiment  Xo.  1  ((Uycstion  experiment  No.  11). 


Breakfast. 

Dinner. 

Supper. 

Egss,  abont 

Grams. 
100 
15 

100 
100 
•JO 
300 

Grams. 
121 
20 
300 
150 
150 

Gram,*. 
75 

Butter 

Butter 

Milk 

600 

Milk 

Milk 

100 

Bread 

The  digestion  experiment  was  of  longer  duration  than  the  respiration 
expeiiiiiont.  It  began  with  breakfast  February  15,  181)0,  and  ended 
with  dinnor  February  10,  covering  four  and  two-thirds  days  and  includ- 
ing 14  meals.  Of  this  period  two  and  one  fourth  days  (11  a.  m.  Feb- 
ruary 17  until  the  close  of  the  experiment)  were  i^assed  in  the  respira- 
tion chamber.  Tlie  weight  of  the  subject  (without  clothing)  at  the 
beginning  of  the  latter  period  was  Ofi.D  kilograms  (147^  i^ounds).  The 
total  amount  of  each  iood  consumed  and  of  the  feces  excreted  during 
tlie  whole  experimental  period,  the  composition  and  fuel  values  of  food 
and  fece."*,  and  the  amount  and  percentage  of  each  nutrient  digested  are 
shown  in  Table  3. 


T.\I!LK  3. 


-Food  eaten  and  digested  during  the  whole  experimental  period,  43  days  {diges- 
tion experiment  No.  11). 


Labo- 
ra- 
tory 

n  am- 
ber. 


26'..6 
2695 

4238 
422S 
4227 
2697 
2693 
2694 
2722 


Kind  of  food. 


Beef,  fried 

E;rg8,  boiled 

Butttr 

Cll(M-H.! 

Milk 

Crackers,  milk  . . 

Bread,  rye 

Potatoes,  boiled  . 
Sugar 


2764      VcxfM 


Total. 


Amount  digested. 
Fuel  value  urea 


Net  amount  digented  . 
Per  cent  digewted 


Weight 

for 
experi- 
ment. 


Grams. 
C04 
497 
175 
300 
4,  400 
396 
1,250 
755 
100 


Total 
organic 
matter. 


Grams. 
240 
127 
153 
158 
582 
368 
746 
140 
100 


2, 607 
71 


2,536 


97.3 


Protein 

(NX6.25.) 


Grams. 
175 
64 
2 
80 
159 
44 
115 
17 


656 
26 


96.1 


Fat. 


Grams. 
59 
56 
151 

74 
183 

48 
2 
1 


574 
15 


97.4 


Carbo- 
hvdrates. 


4 

240 
270 
629 
122 
100 


1, 377 
30 


1,347 


97.8 


Fuel 
value, 
deter- 
mined. 


Calories. 

1,506 

943 

1,421 

1,266 

3,078 

1,852 

3,351 

594 

399 


15,010 
500 


14,  510 
535 


13, 975 
93.1 


42 

The  amount,  composition,  and  fuel  value  of  the  food  during  the  two 
and  one-fourth  days  (Februaiy  17,  11  a.  m.,  to  February  19,  5  ]).  m.) 
passed  in  the  respiration  chamber  are  shown  in  the  following  table: 

Table  4. — Food  eaten  during  the  period  in  the  respiration  chamler,  2^  days  {respiration 

experiment  No.  1). 


Labo- 
ra- 
tory 

num- 
ber. 

Kind  of  food. 

Weight 
per  day. 

Nitro- 
gen. 

Carbon . 

Protein 

(NX  6.25.) 

Fat. 

Carbo- 

by- 
drates. 

Fuel  \ 

Deter- 
mined. 

ralnes. 

Calcu- 
lated. 

2696 

One  day,  3  meals. 
Beef,  fried 

Grams. 

121 

98 

35 

75 

1,  000 

100 

250 

150 

20 

Grams. 
5.61 
2.03 
.05 
3.22 
5.80 
1.78 
3.07 

Grams. 
25.70 
14.16 
22.  62 
25.  07 
72. 70 
44.00 
64.62 
12.00 
8.41 

Grams. 
35.1 
12.7 
.3 
20.1 
30.3 
11.1 
23.0 
3.2 

Grams. 
11.8 
11.1 
30.2 
18.4 
41.5 
12.3 
.4 
2 

Gramas. 
1.3 

.9 
54.5 
09.6 
125.8 
24.3 
20.  0 

Calories. 
302 
186 
284 
285 
836 
408 
670 
118 
80 

Calories. 
308 

2695 

181 

4238 

283 

4228 

285 

4227 

Milk           ..           

809 

2697 
2693 

Crackers,  milk 

401 
645 

2694 
2722 

Potatoes,  boiled 

119 

82 

Total 

22.68 

289.  28 

141.8 

125.9 

296.4 

3,229 

3,173 

For  dinner,  Feb.  19. 

2696 

120 
20 
300 
150 
150 

5.57 

.03 

1.74 

2.20 

.52 

25.49 
12.93 
21.81 
38.77 
12.00 

34.8 

.2 

10.9 

13.8 

3.2 

11.7 

17.3 

12.4 

.2 

.2 

1.3 

"ie.'s' 

75.4 
24.3 

299 
162 
251 
402 
118 

306 

4238 
4227 
2693 

Butter 

Milk 

162 
243 
387 

2694 

Potatoes,  boiled 

Total 

119 

10.06 

111.  00 

62.8 

41.8 

117.3 

1,  232 

1,  217 

Grand  total,  2i 

55.42 

689.  56 

319.2 

293.6 

710.1 

7,690 

7,563 

On  the  days  which  the  subject  passed  in  the  respiration  chamber  the 
urine  was  collected  also.  In  this  and  the  following  experiment  it  was 
not  collected  after  the  subject  left  the  apparatus,^  The  urine  was  col- 
lected from  G  p.  m.  on  the  day  before  the  respiration  experiment  began 
to  5  p.  m.  on  the  day  the  experiment  ended.  As  the  experiment  began 
at  noon,  the  weights  of  urine  excreted  have  been  recalculated  so  as  to  give 
the  weights  from  noon  to  noon,  instead  of  from  0  p.  m.  to  G  p.  m.  In 
doing  this  it  was  assumed  that  the  amount  secreted  was  uniform  from 
hour  to  hour,  and  that  the  amount  for  the  original  period,  from  6  p.  m. 
to  G  p.  m.,  could  be  divided  into  two  parts  proportional  to  the  time,  one 
part  being  the  amount  from  G  p.  m.  to  12  m.  the  next  day,  the  other 
the  amount  from  12  m.  to  6  p.  m.  The  amount  for  the  -short  period  of 
six  hours,  from  12  m.  to  6  p.  m.  of  one  day,  was  then  added  to  the  amount 
for  the  longer  period  of  eighteen  hours,  from  G  p.  m.  to  12  m.  of  the 
following  day,  thus  giving  the  total  weight  for  the  twenty-four  hoars 
from  12  m.  to  12  m.  Of  course,  this  allows  for  no  lag  in  the  urine 
(see  page  35),  but  the  error  thus  introduced  is  probably  not  very  great. 
The  subject  had  been  doing  light  manual  labor  before  entering  the 
apparatus,  and  did  no  Avork  during  the  exi)eriment.  There  may  have 
been  a  slightly  larger  amount  of  nitrogen  in  the  urine  of  the  first  day 
of  the  experiment  than  was   actually  metabolized  during  that  day. 

^In  experiments  3  and  4  it  was  collected  for  some  time  after,  as  stated  in  the 
descriptions  of  those  experiments. 


43 

Such  excess  might  have  oeen  due  to  the  metabolizing  of  a  larger 
quantity  of  nitrogen  during  the  day  before  the  subject  entered  the 
apparatus.  Thus  it  is  to  be  observed  that  the  weight  of  uitrogeu 
eliminated  in  all  of  the  experiments,  with  the  exception  of  the  third, 
is  slightly  smaller  on  the  second  day  than  on  the  lirst. 

The  amount  of  urine  and  feces  excreted  while  the  subject  was  in  the 
resi)irati<»n  chamber  and  the  nitrogen  and  carbon  content  and  fuel 
value  of  each  are  given  in  the  following  table: 

Table  5.—Xitro(i)n    and  carhmi  and  fuel  raliie  of  iirhir  mid  feces  (respirafion  experi- 
ment jN'o.  J). 


I'riiie  aud  feces. 


Frine  (February  17-18,  12  m.  to 
12  in.) 

Uriue  (February  18-19,  12  m.  to 
12  m.) 

Urine  (February  19,  12  ni.  to  5 
p.ui.) 

ToUl 

Fece.s  (average  for  1  day) , 

Total,  2  daj's 


Auiount. 


Grains. 
1,395 


1,  ,313 
260 


2,968 
21.9 
43.8 


Nitrogen. 


Per  et.    Orams. 
1.45        20.23 


1.45 
1.45 


19.04 
3.77 


43.04 
.95 
1.82 


Carbon. 


Per  ct.    Orams. 
0.84  I     11.72 


11.  03 
2.18 


24.  93 
8.98 
17.90 


Fuel 

value  per 

gram. 


Calories. 
0.110 


.110 
.110 


Total 

fuel 

value. 


Calories. 
154 


145 

28 


327 
107 
214 


The  carbon  dioxid  produced  by  the  subject  was  measured  during  the 
period  j>assed  in  the  respiration  chamber.  For  convenience  in  collect- 
ing samples  the  day  of  twenty-four  hours  was  divided  into  several 
periods.  The  volume  of  air  j)assiug  through  the  respiration  chamber, 
the  amount  of  carbon  dioxid  it  contained  per  liter  on  entering  and  on 
leaving  the  chamber,  and  the  total  amount  excreted  by  the  subject,  as 
well  as  the  total  amount  of  carbon  in  the  excreted  carbon  dioxid  are 
shown  in  the  following  table: 

Tablk  6. — Carbon  dioxid  produced  in  respiration  experiment  No.  t. 


Date. 


February  17,  12in.,  to 
FebniiirylS,  12iM. 


February  18.  12  tn.,  to 
February  19,  12  in. 

February  19,  12  -n.  \*t 
5  p.  in. 


Period. 


Ventila- 
tion (vol- 
ume of 
air). 


Liters. 
fl2ui.to7p.m '      21,724 


'7  ji.  III.  to  2  a.  Ill 

|2  H.  III.  to 9  a.  m ' 

9  a.  III.  to  3  p.  in.. .' 

3  p.  Ill  tf)  10  p.m.. . 

10  |i.  m.  to  4  a.  m . . 

4  a.  111.  to  11  a.  III.. 

ill  a. ni.  to  5 p.m.. 


21,  094 
20,  566 

20,  052 

20,  300 
19,  4.50 
21,227 

17, 933 


CO-i  per  liter. 


In  incom-  In  outgo- 
ing air.      in g  air. 


Mg. 

0.51 

.61 
.59 


Mg. 

12.48 

10.28 
8.01 


13.39 
9.  75 
9.3(1 

12.74 


(jiven 
otr  by 
subject. 


Mg. 

11.97 

9.67 
7.42 

11.03 

12.81 
9.17 
8.70 

12. 15 


Total 
weight 
CO^  ex- 
haled by 
subject. 


Grains. 

(     a  60. 4 

I      260. 0 

203.  9 

152.7 

/      116.6 

I    6116.6 

260. 4 

178.4 

184.7 

/         :t6.3| 

I  cisi.ej 


Total 
weight  C 
exhaled 
in  CO2. 


Grains. 
216.5 


211.7 
49.5 


aTho  air  in  the  reHpiration  chamber  at  the  clo8^^  of  the  (^xiH^riiiient  coiitaiiicfl  more  COj  than  at  the 
beginning.  AiialVHeM  ol  Haiiiples,  knowing  the  volume  of  air  in  Ilie  <liaml)er,  Hhowed  Ibis  diirerelicu 
ill  amount  to  bi- approximat<'ly  60.4  graiiiH.  It  is  a.ssuiiK-d  that  tliis  increa.se  took  place  during  the 
Hint  iweiityfour  hours,  on  wliiVb  assum|itlon  00.4  grams  of  ( 'O.^  <!X  baled  remained  in  t  ho  aji|)ariitus, 
and  hence  was  not  deducted  and  measured  by  the  regubir  analyses.  Accordingly  thin  amount  of  CO.^ 
is  athjixl  to  the  amount  found  bv  th4-.  analysis  for  thi-.  tlrst.  twenty-four  hours. 

fcOf  the  jMrriod  from  0  a.  m  to  3  p.  m.,'  half  belongs  to  the  lirHl  aud  hull'  to  the  second  day  of  the 
cx|M;rinii'nt. 

eilf  the  periisl  from  1 1  a.  m  to  5  p.  m..  tUi-  lirst  hour  belongs  to  the  second  day  and  the  remainder  to 
the  fracUou  uf  the  third  <biy  of  Ibo  experiment . 


44 

From  the  data  of  Tables  4,  5,  and  G  the  balance  of  income  and  outgo 
of  carbon  and  nitrogen  is  computed  with  results  shown  in  Table  7. 

In  this  and  in  the  following  experiment  the  subject  passed  two  and 
one-fourth  days  (fifty-four  hours)  in  the  respiration  chamber,  and  the 
nitrogen  of  the  urine  and  the  carbon  of  the  carbon  dioxid  exhaled 
were  determined  for  this  length  of  time.  The  number  of  meals  taken, 
however,  was  seven,  which  included  two  whole  days  and  dinner  on  the 
third  day.  It  is,  of  course,  impossible  to  say  how  much  of  the  nutri- 
ents and  energy  of  the  food  eaten  for  dinner  at  12  o'clock  would  be 
utilized  in  the  body  before  the  close  of  the  experiment  at  5  o'clock. 
There  is  a  similar  uncertainty  as  to  how  much  of  the  outgo  of  feces 
should  be  accredited  to  this  quarter  day.  Accordingly,  tlie  results  of 
these  two  experiments  have  been  calculated  for  the  two  whole  days, 
the  fraction  of  a  day  at  the  close  of  the  experiment  being  left  out  of 
account. 


Table  7. 


-Balance  of  income  and  outgo  of  nitrogen  and  carhon  (respiration  experi' 
mcnt  No.  1). 


Nitrogen. 

Carbon. 

Fuel  value. 

Date. 

In 

food. 

In 
urine. 

In 
feces. 

Gain. 

In 

food. 

In 
urine. 

In 
feces. 

In  res- 
pira- 
tory 
prod- 
ucts. 

Gain. 

Of 
food. 

Of 
urine. 

Of 

feces. 

February  17-18, 12  m. 
to  12ni 

Gms. 
22.7 

22.7 

Qms. 
20.2 

19.0 

Qms. 
0.9 

.9 

Qms. 
1.6 

2.8 

Gms. 
289.3 

289.3 

Gms. 
11.7 

11.0 

Qms. 
9.0 

9.0 

Gms. 
216.5 

211.7 

Gm,s. 
52.1 

57.6 

Calo- 
ries. 
3,229 

3,229 

Calo- 
ries. 
154 

145 

Calo- 
ries. 
107 

February  18-19, 12  m. 

107 

Total,  2  days... 

45.4 

39.2 

1.8 

4.4 

578.6 

22.7 

18.0 

428.2 

109.7 

6,458 

299 

214 

As  explained  on  p.  38,  the  amount  of  protein  gained  or  lost  by  the 
body  may  be  computed  from  the  gain  or  loss  of  nitrogen,  and  the  amount 
of  fat  stored  or  lost  by  the  body  maybe  computed  from  the  gain  or  loss 
of  carbon,  taking  into  account  also  the  carbon  in  the  protein  gained  or 
lost.    The  resultS'of  such  computations  are  given  in  the  following  table: 


Table  8. — Gain  or  loss  of  protein  and  fat  in  respiration  experiment  No.  1. 


Date. 

Nitrogen 
gained.; 

Protein 
gained. 

Total  car- 
bon 
gained. 

Carbon  in 
protein 
gained. 

Algebraic 
difference  be- 
tween total 
carbon  and 
carbon  in  pro- 
tein (=M). 

Fat 

gained 

(M-- 0.765). 

February  17-18, 12  m.  to  12  m 

February  18-19, 12  m.  to  12  m 

Grams. 
1.6 

2.8 

Grams. 
10.0 
17.5 

Grams. 
52.1 
57.6 

Grams. 
5.3 
9.3 

Grams. 
46.8 
48.3 

Orams. 
6L2 
63.1 

Total,  2  days 

4.4 

27.5 

109.7 

14.6 

95.1 

124.3 

The  table  indicates  that  during  the  two  days  of  the  experiment  27.5 
grams  of  protein  and  124.3  grams  of  fat  were  stored  up  in  the  body. 


45 

RESPIRATION  EXPERIMENT  No.  2  (DKiESTION  EXPERIMENT  No.  12). 

This  experiment  was  made  with  the  same  subject  and  under  the  same 
conditions  as  experiment  No.  1.  The  digestion  experiment  began  with 
brealifast  February  24, 1800,  and  ended  with  dinner  February  28,  mak- 
ing 14  meals,  or  four  and  two-thirds  days.  The  period  from  11  a.  m., 
February  2G,  to  the  close  of  the  experiment,  at  5  p.  m.,  February  28, 
covering  two  and  one-fourth  days,  and  inchiding  7  meals,  was  spent  in 
the  respiration  chamber.  Tlie  weight  of  the  subject  at  the  beginning 
of  the  experiment  (without  clothing)  was  07.5  kilograms  (148^  pounds). 
The  daily  menu  was  as  follows : 

Table  9. — Daily  menu,  respiration  experiment  Xo.  2  {digestion  experiment  Xo.  12). 


Breakfast. 


Eggs,  aliont. 

Butter 

Milk 

Bread 

Sugar 

Cofl'ee,  about 


Grains, 
100 
15 
100 
100 
20 
300 


Dinner. 


Cooked  meat 

Butter 

Milk 

Bread 

Potatoes  .... 


Grams. 
121 
20 
300 
150 
150 


Supper. 


Clicese 

Milk 

Milk  crackers 

Sugar 

Co3ee,  about  . 


Graing. 

75 
100 
100 

20 
300 


Tables  10  and  11  show  the  amounts,  composition,  and  fuel  values  of 
tlie  food  and  feces  and  tlie  coefficients  of  digestibility  for  the  whole 
l)eriod  (four  and  two-thirds  days)  and  the  amount,  composition,  and 
fuel  value  of  the  food  during  the  period  in  the  respiration  chamber 
(two  and  one-fourth  days). 

Tablk   10. — Food  eaten  and    digested  during  the  whole  experimental  period,  4^    days 
{digestion  experiment  Xo.  12). 


Labo- 
ra- 
tory 

IIUUl- 

ber. 


Kind  of  food. 


Weight 

for 
experi- 
ment. 


Total 
organic 
matter. 


Protein 

(NX  0.25) 


Fat. 


Carbo- 
hydrates 


Fuel 
value, 
deter- 
mined. 


2699 
2»;98 
4_'3'.t 
4237 
4240 
2701 
2703 
27<>0 
2722 


Beef.  friPtl 

Ek-s,  boiled 

Hiitter 

Cbeeso 

Milk 

Craekers,  milk. . 

Bread,  rye 

Potat^ies,  boiled. 
Sugar 


2760     Feces 


Total. 


Anioiinldigestcd- 
Fuel  value  urea 


Net  amount  digested. 
Per  cent  digcstetl 


Grams. 
515 
49H 
175 
300 

L',  400 
400 

1,  130 

eoi 

180 


Grams. 
217 
127 
151 
1G9 
321 
3(iH 
CCl 
146 
180 


rains. 
160 
62 
2 
70 
81 
42 
102 
30 


Grains. 

57 

65 

149 

81 

108 

49 

2 

1 


Grams. 


12 
132 

277 
.557 
115 
180 


Calories. 
1,  4.30 
1,017 
i,  432 
1,266 
1, 973 
1,872 
2,961 
638 
718 


2,340 
81 


555 
46 


512 
15 


1,273 
20 


13,  313 
542 


2, 2.59 


1,253 


12,771 
448 


91.7 


97.1 


12,  323 
92.6 


46 

Tai'.le  11. — Food  eaten  and  digested  during  the  period  in  the  respiration  chamher,  2J  days 
{resjnration  experiment  Xo.  2). 


Labo- 
ra- 
tory 
num- 
ber. 


2699 
2698 
4239 
4237 
4240 
2701 
2703 
2700 
2722 


2699 
4239 
4240 
2703 
2700 


Kind  of  food. 


One  day,  3  meals. 


Beef,  fried 

Eggs,  boiled 

Butter 

Clieese 

Milk 

Crackers,  milk . . 

Bread,  rye 

Potatoes,  boiled . 
Sugar 


Total. 


For  dinner,  Feb.  : 


Beef,  fried 

Butter 

Milk 

Bread,  rye 

Potatoes,  boiled . 


Total. 


Grand  total,  2i 


Weight 
per 
day. 


Oranns. 

121 

101 

35 

75 

500 

100 

228 

150 

40 


31 
20 
300 
80 
61 


Nitro- 
gen. 


Grams. 
5.87 
2.01 

.00 
3.05 
2.70 
1.67 
3.26 

.54 


1.50 

.03 

1.62 

1.14 

.22 


4.51 


Carbon. 


Grains. 
27.83 
15.10 
23.24 
26.85 
33.95 
44.01 
58.44 
14.31 
16.82 


260.  55 


7.13 
13.28 
20.37 
20.50 

5.82 


67.10 


Protein 

(NX6.25). 


Grains. 
36.7 
12  6 
.3 
19.1 
16.9 
10.4 
20.4 
3.4 


9.4 

.2 

10.1 

7.2 
1.4 


28.3 


267.9 


Fat. 


Grams. 
13.4 
13.1 
29.9 
20.3 
22.5 
12.2 
.  5 
.1 


Carbo- 
hy- 
drates. 


Grams. 
0.9 


3.4 
17.1 
13.5 


3.0 
27.5 
68.5 
111.8 
29.6 
40.0 


281.3 


16.5 
39.2 
13.0 


631.5 


Fuel  values. 


Deter- 
mined. 


Calories. 
337 
206 
286 
317 
411 
468 
594 
145 
160 


2,924 


86 
164 
247 

208 
59 


6,612 


Calcu- 
lated. 


Calories. 
330 
198 
280 
305 
415 
452 
575 
141 
164 


2,f 


84 
160 
249 
202 

61 


6,476 


The  amounts  of  urine  and  feces  excreted  during  the  period  in  the 
respiration  chamber  and  the  nitrogen  and  carbon  content  and  fuel 
value  of  each  are  shown  in  the  following  table : 


Table  12. 


-Nitrogen  and  carbon  and  fuel  value  of  urine  and  feces  (respiration  experi- 
ment No.  2). 


Labo- 
ra- 
tory 

num- 
ber. 

Urine  and  feces. 

Amount. 

Nitrogen. 

Carbon. 

Fuel 

value  per 

gram. 

Total 

fuel 

value. 

5018 

Urine  (February  26-27,  12  m.  to 
12  m.) 

Grams. 
969 

913 

190 

Per  ct. 
1.92 

1.92 

1.92 

Grams. 
18.60 

17.53 

3.65 

Per  ct. 
1.52 

1.52 

1..52 

Grams. 
14.73 

13.88 

2.89 

Calories. 
0.169 

.169 

.169 

Calories. 
164 

Urine  (February  27-28,  12  m.  to 
12  m.) 

154 

Urine  (February  28,  12  m.  to  5 

32 

Total 

2,072 
23.8 
47.6 

"'e.'es' 

39.78 
1.58 
3.16 

"41.49 


3L50 

9.87 
19.74 

350 

276.5 

Feces  (average  for  1  day) 

Total,  2  days 

4.886 

116 

232 

47 


The  carbon  dioxid  produced  during  the  period  in  the  respiration 
chamber  is  shown  in  the  followiug  table  : 

Table  13. — Carbon  dioxid  produced  in  respiration  experiment  iVo.  2. 


Period. 

Ventila- 
tion 
(volume 
©fair). 

CO2  per  liter. 

Total 

Total 

Date. 

In  incom- 
ing air. 

In  outgo- 
ing air. 

Given 

otf  by 

subject. 

Me^dbv     -^^d 
subject.      '°  ^^•^• 

Febmary  26. 12 m.,to 
February  27, 12  m. 

February  27, 12  m.,  to 
February  28, 12m. 

February  28, 12  m.  tol 
5  p.  m.                         / 

fl2m.to6p  m 

le  p.m.  to  1  .a.m... 

1  a.m.  to  7  a.  m 

7  a.m.  to 2  p.  m 

2  p.m.  to 9  p. m 

9  p.m. to  4a. m 

4  a.  m  to  10.30 a.m. 

10.30a.m.to5p.m. 

Litert. 
21,064 

20,  932 
20, 686 

21,  880 

22,  492 
22, 900 
22,  216 

21,  607 

Mg. 

0.56 

.57 
.59 

.60 

.54 
.00 
.61 

.58 

Mg. 

11.63 

11.50 
8.06 

11.20 

12.  Co 
8.45 
9.16 

10.92 

Mg. 

11.07 

10.93 
7.47 

10.60 

12.11 
7.85 
8.55 

10.34 

Grams.  \ 
1  53.  2 
233.2 
228.8 
154.5 
/       165. 6 
I      ■•'66.3 
272.  3 
179.8 
190.0 
f        52.1^ 
\    »171.3/ 

Grains. 
227. 8 

207. 3 
46.8 

'  The  air  in  the  respiration  chamber  at  the  close  of  the  experiment  contained  more  CO2  than  at  the 
l>eginning.  Analyses  of  samples,  comijured  with  the  volume  of  air  in  the  chamber,  showed  tliis 
ditierenee  in  amount  to  be  api)roxiniately  53.2  grams.  It  is  as.sumed  tliat  this  iucrejwe  took  ))laee 
during  the  tirst  twenty-four  hours,  on  wliich  assumption  53.2  grams  of  COj  exhaled  remained  in  the 
apparatus,  and  hence  was  not  deducted  and  measured  by  the'  regular  analyses.  Accordingly,  this 
amount  of  CUj  is  added  to  the  amount  found  by  the  analysis  for  the  first  twenty-four  hours. 

-Of  the  period  from  7  a.  m.  to  2  p.  m.,  five  hours  belong  to  the  first,  and  the  remainder  to  the  second 
day  of  the  experiment. 

5  Of  the  period  from  10.30  a.  m.  to  5  p.m.,  the  tirst  one  and  one-half  hours  belong  to  tho  second 
day  and  the  remainder  to  the  fraction  of  the  third  day  of  the  experiment. 

Table  14  shows  the  balance  of  income  and  outgo  of  nitrogen  and  car- 
bon.   The  figures  are  computed  from  data  given  in  Tables  11, 12,  and  13. 

Table  1-4. — Balance  of  income  and  outqo  of  nitrogen  and  carion  {respiration  experiment 

No.  2). 


Kitrogen. 

Carbon. 

Fuel  value. 

Date. 

In 
food. 

In 
urine. 

In 

feces. 

Gain 

(+)">■ 
loss 

(-)• 

In 
food. 

In 
urine. 

In 
feces. 

In  res- 
pira- 
tory 
prod- 
ucts. 

Gain 

(+)  or 

loss 

Of 
food. 

Of 
urine. 

Of 
feces. 

Febmary  26-27.  12 
m.  to  12  111 

February  27-28,  12 
m.  to  1*2  in 

Gms. 
19.2 

19.2 

Gms. 
18.6 

17.5 

Gms. 
1.6 

1.6 

Gms. 
—1.0 

H0.1 

Gms. 
260.6 

260.6 

Gm^. 
14.7 

13.9 

Gms. 
9.9 

9.9 

Gms. 
227. 8 

207.3 

Gms. 
+  8.2 

+29.5 

Galn- 
ries. 
2, 924 

2,924 

C'alo- 

rie.i. 

164 

154 

Calo- 
ries. 
116 

116 

Total,  2  days. 

38.4 

36.1  j    3.2  1  —0.9 

521.2 

28.6 

19.8 

435.1 

+37.7 

5,848 

318 

232 

The  calculated  gains  or  losses  of  protein  and  fat  are  show  n  in  Table  15. 
Tablk  15. — Gain  or  loss  of  i>roiein  and  fat  {respiration  experiment  No.  2). 


Date. 

Nitrogen 
gained  (  +  ) 
orloBt(— ). 

Protein 
gained  (  1  ) 
orlost(— ). 

Grams. 
-6.3 
+  0.6 

Tolal 
carbon 
gained. 

Carbon  in 

protein 
gained  (  +  ) 
or  lost  (— ). 

Algebraic 

dili'erenee 
between 

t^ital  car- 
bon and 

carbon  in 
protein 
(-M). 

Fat 
gained 
(M  : 
0.765). 

February  26-27, 12  m.  to  12  m  . . . 
February  27  28, 12  in.  to  12  m  . .. 

Grams. 
-1.0 
+0.1 

Grams. 
1-  8.2 
129.5 

Grams. 
—3.3 
10.3 

Grams. 

1  11.5 
+29.  2 

Grams. 
+  1.5.0 
1  38.  2 

Total,  2  dayfl .. .... 

-0.9 

—5.7 

+37.7 

-3.0 

+  40.7 

+53. 2 

48 

RESPIEATIOK  EXPERIMENT  No.  3  (DIGESTION  EXPERIMENT  No.  13). 

In  this  experiment  the  methods  had  been  considerably  improved  and 
the  force  of  observers  enlarged,  advantage  being  taken  of  the  experi- 
ence gained  in  the  two  previous  experiments.  The  subject  was  a 
chemist  (O.  F.T.)  24  years  old.  The  experiment  began  with  breakfast 
March  13  and  ended  with  breakfast  March  21, 1896,  thus  covering  eight 
and  one- third  days  and  including  25  meals.  The  respiration  experiment 
proper  covered  the  5  days  with  15  meals  from  11  a.  m.  March  6  to  11 
a.  m.  March  21,  inclusive.  The  weight  of  the  subject  at  the  beginning 
of  the  experiment  (without  clothing)  was  57.2  kilograms  (126  pounds). 
The  subject  was  accustomed  to  rather  less  muscular  labor  than  tlie 
subject  of  the  first  two  experiments.  Pie  was  also  rather  lighter  in 
weight.  During  the  experiment  he  performed  as  little  muscular  labor 
as  possible.  He  passed  the  time  in  resting,  with  light  reading  for 
diversion.  The  diet,  which  he  himself  selected,  was  somewhat  smaller 
than  that  of  the  subject  of  the  first  two  experiments  and  furnished 
considerably  less  protein  and  energy. 

The  daily  menu  throughout  the  experiment  was  as  follows: 

Table  16. — Daily  menu,  respiration  experiment  No.  3  (digestion  experiment  No.  13). 


Breakfast. 


Eggs > 

Butter 

Milk 

Bread   

Sugar 

Apples 

Tea  or  coffee,  about 


Or 


ams. 

113 
10 

100 
75 
20 
85 

300 


Dinner. 


Cooked  beef 

Butter 

Milk 

Bread 

Sugar 

Potatoes 

Peaches  or  pears  . . . 
Tea  or  coffee,  about 


Grams. 

95 

10 

60 

75 

20 

130 

150 

300 


Supper. 


Milk 

Bread  

Sugar 

Peaches  or  pears 


Qrams. 

500 

125 

10 

200 


The  amounts,  comi)osition,  and  fuel  values  of  the  food  and  feces  and 
the  coefficients  of  digestibility  for  the  whole  period  (eight  and  one-third 
days),  and  the  amount,  composition,  and  fuel  value  of  the  food  for  the 
period  in  the  respiration  chamber  (five  days)  are  shown  in  the  follow- 
ing tables: 

Table  17. — Food  eaten  and  digested  during  the  whole  experimental  period,  d>\  days  {diges- 
tion experiment  No.  IS). 


Labo- 
ra- 
tory 
num- 
ber. 


2704 
2705 
4248 
4247 
2724 
2708 
2709 
2707 
2706 
2722 


Kind  of  food. 


Beef,  fried 

Eggs,  boiled 

Butter 

Milk 

Bread 

Potatoes,  boiled  . 

Apples 

Peaches 

Pears 

Sugar 


Total. 


Weight 

for 
experi- 
ment. 


Qrams. 

766 

904 

170 

5,380 

2,275 

2,300 

755 

1,400 

1,400 

400 


.^^^±     Protein 

Se"   (^><«-25) 


Grams. 
289 
256 
152 
717 
1,367 
554 
99 
146 
277 
400 

4,257 


Gramt. 

227 

137 

2 

178 

187 

52 

2 


Grams. 

62 

119 

150 

245 

30 

3 

1 

2 

1 


Carbo- 
hydrates. 


Grams. 


294 
1,150 
499 
96 
136 
273 
400 

2,848 


Fuel 
value, 
deter- 
mined. 


Calorics. 
1,857 
1,919 
1,434 
4,341 
6,222 
2,373 
413 
666 
1,121 
1,595 

21, 941 


49 


Tai-.le  17. — Food  ealin  and  d'ujisltd  dnrimj  the  whoh  exjiirimviitdl  period,  etc. — Cont'd. 


Labo- 
ra- 
tory 

u  um- 
ber. 

Weight 

Kiud  of  foo.1.                            •'"^'  . 
experi- 

iiieut. 

Total 
organic 
matter. 

Protein 

(K  A  6.25). 

Fat. 

Carbo- 
hydrates. 

Fuel 
value, 
deter- 
mined. 

2760 

1    Grains. 
Feces 131 

Gravis. 
97 

Grains. 
44 

Grams. 

20 

Grams. 
33 

Calories. 
628 

4,160 

752  1            59:i 

Fuel  value  urt-a 

654 

Not  aiiionut  digested 

20,  659 
94.2 

Per  cent  digested 

97.7 

94. 5             96. 7 

98.9 

T.VHLK  18. — Food  eatiii  di(riuij  thr period  in  the  rei^piration  chamher,  'i  days  {respiration 

experiment  No.  3). 


Labo- 
ra- 
tory 
num- 
ber. 


2704 
2705 
4248 
4247 
2724 
2708 
2709 
2707 
2706 
2722 


Kind  of  food. 


Five  days,  IS  meals. 


Beef,  fried 

EggH,  boiled 

Butter 

Milk 

Bread 

Potatoes,  boiled  . 

Apples 

Peaches 

Pears 

Sugar 


I  Total 

:  Quantities  per  day 


Weight 

for     I 

5  days. 


Nitro- 


Grams. 

481 

502 

100 

3,  300 

1,875 

1,350 

425 

700 

1,050 

230 


Grams. 

22. 75 

12.10 

.14 

17.49 

18.01 

4.99 

.17 

.63 

.42 


70.  71) 
15.34 


Carbon. 


Grams. 
97.43 
77.40 
67.07 
203.  60 
355. 10 
130.  70 
23.76 
34.09 
85.  57 
96.74 


Protein 
(XX6.25). 


Grams. 

142.  2 

75.6 

.9 

109.2 

112.9 

30.5 

1.0 

5.0 

2.2 


1,171.52 
234.  30 


479.5 
95.9 


Fat. 


Grams. 

38.7 

66.  3 

88.4 

150.0 

18.0 

1.5 

.7 

1.3 

1.0 


365.9 
73.2 


Carbo- 

li.V- 
drates. 


Grains. 


180.5 
695.4 
293.  0 
54.0 
85.0 
170.7 
210.0 


1,  688.  6 
337.7 


Fuel  values. 


Deter- 
mined. 


Calories. 

1,166 

1,066 

843 

2,663 

3,760 

1,393 

232 

333 

841 

917 


13,  214 
2,643 


Calcu- 
lated. 


Calorics. 

1,  145 

1,  032 

826 

2,737 

3,644 

1,383 

235 

388 

718 

861 


12,969 
2,594 


Table  19  shows  the  amounts  of  urine  and  feces  excreted  during  the 
period  in  tlio  resi)iratiou  chamber  and  the  nitrogen  and  carbon  content 
and  fuel  value  of  each.  In  this  table  a  12-hour  lag  is  allowed  in  calcu- 
lating the  urine  and  feces  (see  p.  35).  In  the  light  of  the  results 
obtained  in  the  succeeding  experiment  this  seems  to  be  more  nearly- 
accurate  than  tlie  0-hour  lag.  The  time  allowed  for  lag  is,  however, 
probably  of  comparatively  little  importance,  as  the  diet  and  occupation 
were  very  nearly  uniform. 

Table  19. — Xitrogeu  and  carbon  and  fuel  values  of  urine  and  fecea  {respiration  experi- 
ment No.  3). 


tory 
nnrii- 
bcr. 


5020 


l'rin«  and  feces. 


Urino  (March  16-17,  0  a.  m.  to 

«a.  m.) 

trine  (Marcli  17-18,  0  a.  m.  to 

6  a.  ni.) 

I'rine  (.Vlarch  18-19,  6  a.  ni.  to 

6  a.  ni.) 

I'rine  (March  19-20,  0  a  ni.  to 

6  a.  m.) 

Urine  (Marcli  20-21,  6  a.  m.  U) 

6  a.  m.) 


Total 

Feces  (ave,rHgc  for  1  day). 
Total,  5  dayH 


Amount. 

Nitrogen. 

Carbon. 

Fuel 

value  per 

gram. 

Total 

fuel 

value. 

Grams, 
974 

Perct. 
1.30 

Oraint. 
12.06 

Per  et. 
0.89 

Grams. 
8.60 

Calories. 
0.101 

Calories. 
98 

1,118 

1.20 

i:i.46 

.89 

9.95 

.101 

113 

1.188 

1.15 

13.61 

.89 

10.  £7 

.101 

120 

1,325 

1.04 

13.69 

.89 

11.79 

.101 

134 

1,.520 

1.00 

15.22 

.80 

13.58 

.101 

l.')4 

6,  131 
16.4 
81.9 

"li.'ai' 

08.64 

.87 

4.37 

"'4i."94' 

54.  55 
0.87 
34.  33 

""i.iwi 

6 19 

79 

395 

2771— No,  44- 


50 

Tlie  amount  of  carbon  dioxid  produced  during  the  period  in  the  res- 
piration chamber  is  shown  in  Table  20. 

Table  20. — Carbon  dioxid pi-ocluced  in  resjnraiion  experiment  No.  3. 


Period. 

Ventila- 
tion 
(volume 
of  air). 

CO2  per  liter. 

Total 
■weight 
CU2  ex- 
haled by 
subject. 

Total 

Date. 

In  incom- 
ing air. 

In  outgo- 
ing air. 

Given 
off  by 
subject. 

■weight  C 
exhaled 
in  COj. 

March  16,  11  a.  ip.,  to 
March  17,  11  a.  ra. 

fll  a.m.  to  6p. m.-  - 

1(3  p.m.  to  la. n) 

11  a.m. to  7  a. m 

Liters. 
37,  462 
41,  560 
37,  360 

0.57 
.56 
.55 

Mg. 
7.57 
6.13 
4.61 

Mg. 
7.00 
5  57 
4.06 

Grams. 
262.2 
231.3 
151.6 

Grams. 
I        220. 9 

,7  a.m.  to  Ip.  m 

36,  470 

.56 

7.19 

6.63 

f    1 164.  9 
\       '  82.  6 

1 

March  17,  11  a.  m.,  to 
March  18,  11  a.  m. 

1  p.m.  TO  8  p.  m 

<8  p.m.  to  3  a.  m 

3  a.m.  to  9  a. m 

40, 150 
29,  620 
27, 470 

.60 
.57 
.62 

7.21 
6.86 
6.88 

6.61 
6.29 
6.26 

265.6 
186.3 
171.9 

I        215. 3 

;9  a.  m.  to  4  p.  m 

31,  500 

.61 

9.89 

9.28 

/      1  83.  2 
\    1208.2 

1 

March  18,  11  a.  m.,  to 
March  19,  11  a.  m. 

J4  p.m.  to  11  p.m... 
1 11  p.  m  to  6  a.  m . . . 

30,  830 
30, 330 

.58 
.63 

9.07 
5.87 

8.49 
5.24 

261.9 
159.0 

I        218. 8 

[e  a.m.  to  Ip.  m 

30,  700 

.62 

8.51 

7.89 

/    1173.1 

\      1  69.  2 

272.9 

216.  6 

220.2 

J 

March  19,  11  a.  m.,  to 
March  20,  11  a.  m. 

1  p.  m.  toSj).  m 

<8  p.m.  to 3  a. m 

3  a.  m.  to  10  a.  m . . . 

33,  210 
33,  930 
33,  820 

.65 
.57 
.53 

8.87 
6.99 
7.04 

8.22 
6.42 
6.51 

\        222. 9 

March  20,  11  a.  m.,  to 
March  21,  11  a.  m. 

Wo  a.m. to  6p.m..- 

^6  p.m.  to  2a. m 

I2  a.m. to  11  a.m... 

37,  060 

40,  990 
44,  093 

.57 

.56 
..52 

8.86 

7.36 
6.54 

8.29 

6.80 
6.02 

/      1  38.  4 

1    1268.8 

278.6 

265.5 

i        221. 7 

1  Of  the  period  from  7  a.  m.  to  1  p.  m.,  March  17,  four  hours  belong  to  the  first  and  the  remainder  to 
the  second  day  of  the  experiment. 

In  like  manner  each  experimental  period  is  made  to  end  at  11  a.  m.,  the  amount  of  COj  eliminated  in 
the  period  in  "tvhich  the  day  ends  being  divided  between  that  day  and  the  next  jiroportionately  to  the 
time. 


The  balance  of  income  and  outgo  of  nitrogen  and  carbon,  as  computed 
from  the  data  given  in  Tables  18,  19,  and  20,  is  shown  in  Table  21: 

Table  21.— Balance  of  income  and  outgo  of  nitrogen  and  carbon  {respiration  experiment 

No.  3). 


Nitrogen. 

Carbon. 

Puel  value. 

Date. 

In 

In 

In 

Gain 

(  +  )  or 

In 

In 

In 

In  res- 
pira- 
tory 
prod- 

Gain 
(+)  or 

Of 

Of 

Of 

food. 

urine. 

feces. 

loss 

food. 

urine. 

feces. 

loss 

food. 

urine. 

feces. 

ucts. 

Calo- 

Calo- 

Calo- 

March 16-17,  11 

Gms. 

Gms. 

.Gms. 

Gms. 

Gms. 

Gms. 

Gms. 

Gms. 

Gms. 

ries. 

ries. 

ries. 

a.m.  to  11  a.m. 

15.3 

12.7 

0.9 

+1.7 

234.3 

8.7 

6.9 

220.9 

—  2.2 

2,645 

98 

79 

March  17-18,  11 

a.  m.  to  11  a.  m. 

15.3 

13.5 

.9 

+0.9 

234.3 

9.9 

6.9 

215.3 

+  2.2 

2,645 

113 

79 

March  18-19,  11 

a.  m.toll  a.  m. 

15.  a 

13.6 

.9 

+0.8 

234.3 

10.6 

6.9 

218.8 

—  2.0 

2,645 

120 

79 

March  19-20,  11 

a.m.  to  11a. m- 

15.  3 

13.7 

.9 

+  0.7 

234.3 

11.8 

6.9 

222.  9 

—  7.3 

2,645 

134 

79 

March  20-21,  11 

a.  m.toll  a.  m. 

15.3 

15.2 

.9 

—0.8 

234.3 

13.6 

6.9 

221.7 

—  7.9 

2, 645 

154 

79 

Total,  5  days 

76.5 

68.7 

4.5 

+3.3 

1, 171. 5 

54.6 

34.5 

1,  099.  6 

—17.2 

13,  225 

619 

395 

51 

The  calculated  gains  and  losses  of  inotein  and  fat  are  shown  in 
Table  22 : 


Taiu.k  22. — daiii  or  loss  of  protein  and  fat  {respiration  experiment  Xo.  3). 


Date. 


March  16-17, 11  a.  m.  to  11  a.  m. 
March  17-18, 11  a.  m.  to  11  a.  m. 
March  18-19. 11  a.  lu.  to  U  a.  m. 
March  19-20, 11  a.  m.  to  11  a.  m. 
March  20-21, 11  a.  m.  to  11  a.  m. 

Total.  5  days 


Nitrogen 
gained 

(+)  or 
lest  (— ). 


Grams. 

+1.7 
+  0.9 
+  0.8 
+  0.7 
—0.8 


+3.3 


Protein 
gained 

(  +  )  or 
lost  (-). 


Grama. 
+  10.6 
+  5.6 
+  5.0 
+  4.4 
—  5.0 


+  20.6 


Total 
carbon 
gained 
(+)  or 
lost  (— ). 


Grams. 

—  2.2 

+  2.2 

—  2.0 

—  7.3 

—  7.9 


-17.2 


I  Algeliraic 
Carbon ini  ditt'erence 
protein     between  tr- 


ained 

■(+)  or 
lost  (— ). 


Grams. 
+  5.6 
+  3.0 

+  2.7 
+  2.3 
—  2.7 


+  10.9 


t.al  carbon 

and  carbon 

in  protein 

(=M). 


Grams. 

—  7.8 

—  0.8 
-  4.7 

—  9.6 

—  5.2 


28.1 


Fat 
gained 

(  +  )or 
lost  (— ) 

(M-- 

0.765K 


Grams. 
—10.2 

—  1.0 

—  6.1 
—12.6 

—  6.8 


-36.7 


-      RESPIRATION  EXPERIMENT  No.  4  (DIGESTION  EXPERIMENT  No.  14). 

The  last  experiment  was  more  detailed  than  the  jirevious  ones  and 
the  observations  were  more  thoroughly  systematized.  The  subject 
was  a  i)hysicist  (A.  W.  S.),  22  years  old,  and  weighed  (without  clothing) 
at  the  beginning  of  the  experiment  69.1)  kilograms  (154  pounds).  The 
exi)eriment  began  with  breakfast  March  19  and  ended  with  dinner 
April  4,  thus  covering  sixteen  and  two-third  days  and  including  tifty 
meals.  During  the  twelve  days  beginning  3  p.  m.  March  23  and  ending 
3  p.  m.  April  4  the  subject  was  in  the  respiration  chamber.  The  twelve 
days  were  divided  into  five  periods,  the  first  of  one  and  five-eighths, 
the  lifth  of  one  and  three-eighths,  and  the  others  of  three  days'  dura- 
tion each.  The  iirst  and  fifth  periods  were  preliminary  and  supple- 
mentary. In  these  preliminarj^  and  supplementary  periods  thus  reck- 
oned as  one  the  subject  did  not  engage  in  any  muscular  or  mental 
work  except  such  reading  and  very  slight  physical  exercise  as  were 
needed  to  pass  away  the  time  comfortably.  For  convenience  in  making 
the  calculations  of  income  and  outgo,  it  was  assumed  that  the  amounts 
of  ingredients  of  food  and  excretory  products  for  the  five-eighths 
and  three-eighths  days,  resiiectively,  made  up  the  corresponding  pro- 
jtortions  of  the  total  daily  amounts.  Of  course  this  assumption  does  not 
affect  the  other  periods  of  the  exjierimcnt.  The  second  period,  of  three 
days  duration,  w^as  devoted  to  mental  labor.  The  subject  engaged  for 
eight  hours  a  day  or  thereabouts  in  the  active  work  of  either  caculating 
results  of  previous  experiments  or  studying  a  German  treatise  on 
physics.  The  mental  application  was  as  intense  as  it  could  well  be 
made.  The  tliird  period,  likewise  of  three  days'  duration,  was  given 
to  nearly  absolute  rest.  During  this  time  the  subject  avoided  muscular 
and  mental  exercise  so  far  as  possible.  During  a  larger  part  of  the 
time  he  n'clined  upon  the  bed.  Of  course  it  was  impossible  to  avoid 
all  intellectual  activity,  but  the  amount  was  made  as  small  as  practi- 
cable.   The  fourth  period  was  one  of  intense  muscular  activity.    A 


52 


pulley  was  attached  to  the  top  of  tlie  chamber.  Over  this  passed  a 
cord.  One  end  of  the  cord  was  attached  to  a  block  of  iron  weighing 
5.7  kilograms  (12.5  x)ounds) ;  on  the  other  end  was  a  handle.  This  pro- 
vided for  active  exercise,  not  only  of  the  arms,  but  also  of  the  legs  and 
other  parts  of  the  body.  The  whole  arrangement  was  quite  similar 
to  some  of  the  forms  of  apparatus  very  commonly  used  for  gymnastic 
exercise.  With  this  the  subject  worked  severely  for  eight  hours  on 
eacli  of  the  three  days,  so  that  at  the  end  of  each  day's  work  he  was 
thoroughly  tired.  He  perspired  very  freely  during  the  working  hours. 
This  period  was  followed  by  the  final  short  period  of  rest. 

In  examining  the  detailed  results  of  the  experiments  it  was  interest- 
ing to  note  that  whatever  had  been  the  occupation  during  the  day  a 
period  of  G  hours'  rest  was  sufficient  to  bring  the  elimination  of  carbon 
dioxid  back  to  a  normal  quantity.  Even  after  the  large  elimination  of 
carbonic  acid  which  accompanied  each  period  of  hard  muscular  work, 
amounting  at  times  to  500  grams  for  six  hours,  the  simple  return  to  rest 
was  followed  almost  immediately  by  a  return  to  the  normal  elimination 
(see  Table  27). 

In  the  case  of  the  elimination  of  nitrogen  in  the  urine,  however,  the 
increase  consequent  upon  hard  muscular  work  or  its  decrease  when  the 
body  was  in  a  state  of  rest  did  not  manifest  itself  until  some  hours 
after  the  muscular  work  began  or  ended  (see  Table  26).  In  the  calcula- 
tions for  Table  26  a  period  of  six  hours  was  allowed  for  the  lag  in  the 
urine.  By  consulting  that  table,  however,  it  will  be  seen  that  the 
increase  of  nitrogen  in  the  urine  following  the  hard  work  of  March  31 
did  not  manifest  itself  until  apparently  thirty  hours  later,  and  did  not 
cease  for  an  equally  long  period  after  the  close  of  active  exercise  on 
the  evening  of  April  2,  during  which  time  the  body  had  been  in  a 
state  of  as  complete  inactivity  as  possible.  This  subject  is  referred 
to  beyond. 

The  character  of  the  food  consumed  during  this  experiment  is  shown 
in  the  following  daily  menu : 

Table  23 — Daily  menu,  respiration  experiment  Ho.  4  {digestion  experiment  No.  14). 


Breakfast. 

Dinner. 

Supper. 

Grams. 
75 
40 
120 
150 
15 
20 

Grams. 
96 
75 

100 
30 

125 

Milk 

Grams. 
500 

250 

Maslied  potatoes 

Butter    

Milk                       

Butter       

Tables  24  and  25  show  the  amounts,  composition,  and  fuel  values  of 
the  food  and  feces  and  the  coefficients  of  digestibility  for  the  whole 
period  (sixteen  and  two-thirds  days)  and  the  amount,  composition,  and 
fuel  value  of  the  food  for  the  period  in  the  respiration  chamber  (twelve 
days). 


i 


53 


Table  24. — Food  eaten  and  digested  during   the  ivhole  experimental  period,   IGJ   days 
(digestion  experiment  No.  14). 


Labo- 
ra- 
tory 

num- 
ber. 


2715 
4249 
4250 
2727 
2726 
2723 
2728 
2725 
2709 
2722 


Kind  of  food. 


Beef,  fried 

Butter 

Milk 

Kri'Md,  wliit^' 

Hre.id,  brown 

Oatmeal 

Hean.s 

Potatoes,  boiled 

Apples 

Sugar 


Feces 


Total. 


Amount  digested. 
Fuel  value  urea 


Not  amount  digested. 
Per  cent  digested 


"Weight 

for 
experi- 
ment. 


Grams. 
1,654 

7C5 
10,  0(10 
2,  550 
4,  000 

680 
2,  040 
1,700 
2,125 

340 


Total 
organic 
matter. 


Grams. 

738 

673 

1,384 

1,016 

2, 022 

609 

516 

393 

279 

340 


8,570 
330 


8,240 


Protein 
(NX6.25). 


Grams. 
506 
8 
351 
235 
232 
117 
141 
42 


1,697 
147 


1,550 


Fat. 


Grams. 

172 

665 

445 

35 

46 

48 

7 

1 

4 


1,423 
58 


1, 365 


Carbo- 
hydrates. 


Grams. 


588 
I,  340 
1,744 
444 
368 
350 
270 
340 


5,  450 
125 


5,325 


Fuel 
value, 
deter- 
mined. 


Galori<'K. 
4,  803 

6,  249 
8,  4.59 

7,  375 
y,  220 
2.  998 
2,  405 
1,681 
1,  102 
1,  35(> 


45,  708 
2,  049 


43,  C,y.) 
1,347 


42,  312 
92.6 


Tablk  25. — Food  eaten  during  the  period  in  the  respiration  chamber,  12  days  {respiration 

experiment  No.  4). 


Labo- 
ra- 
tory 
num- 
ber. 


2715 
4249 
4250 
2727 
2726 
2723 
2728 
2725 
2709 
2722 


Kind  of  food. 


Twelve  days,  36  meals. 


Beef,  fried 

Butter 

Milk 

Bread,  white  . 
Brea<l,  brown. 

Oatmeal 

Beans  

Potatoes 

Apples 

Sugar  


Total. 


Weight 
per  day. 


Grams. 

90 

45 
650 
1.50 
250 

40 
120 
100 
125 

20 


Xitro- 


G  rains. 

5.28 

.08 

3.45 

2.22 

2.32 

1.10 

1.32 

.40 

.05 


Carbon. 


16.22 


Grams. 

22.  33 

30.  08 

39.06 

41.73 

55.67 

16.46 

13.64 

9.77 

6.99 

8.41 


244. 14 


Protein. 


Grams. 

33.0 

.5 

21.5 

13.8 

14.5 

6.9 

8.3 

2.5 

.3 


101.3 


Fat. 


Grams. 

10.0 

39.1 

27.3 

2.0 

2.9 

2.8 

.4 

.1 

.2 


84.8 


Carbo- 
hy- 
drates. 


Grams. 


36.1 
79.2 
109.  0 
20. 1 
21.6 
20.6 
15.  9 
20.0 


328.5 


Fuel  values. 


Deter- 
mined. 


Calories. 
280 
368 
519 
434 
576 
170 
141 
99 
08 
80 


Calcu- 
lated. 


2,741 


Calories. 

273 

367 

520 

420 

553 

171 

138 

99 

69 

82 


2,  692 


Table  20  gives  the  amount  of  urine  and  feces  excreted  during  the 
period  in  the  respiration  chamber  and  the  nitrogen  and  carbon  content 
and  fuel  value  of  each. 


Taislk  26. — Nitrogen  and  carbon  in  urine  and  feces  (respiration  experiment  No.  4). 


Lab- 
ora- 

a 

Fuel 
value 

Total 

lorj' 

Urine  and  feezes. 

S 

Nitrogen. 

(Jarbon. 

fuel 

Kemarks. 

mini' 

value. 

U:t. 

< 

gram. 

Per 

Per 

Cal- 

Cal- 

Gm,s. 

cent. 

Gms. 

cent. 

Gms. 

ories. 

ories. 

rrrrine  (March  23-24,  9  p.  m.  to 
)     12  m.). 

590 

1..53 

9.12 

0.99 

5.90 

0.113 

67 

j Prelim  inary 

.0022 

>     period,    no 

llJrini^  (.March  24-25,   12  in.  to 

772 

1.83 

14.09 

.90 

7.64 

.113 

87 

)     work. 

1     12  m.). 

Irim-  (March  25-2(i,   12  m.  Ut 

815 

1.61 

13. 12 

.72 

5.87 

.083 

«8 

12  ni). 

I'riiie   (M;ircli  26  27,    12  in.   to 

1,230 

1.11 

13.71 

.72 

8,86 

.083 

102 

VMciilal  work. 

5<i2:i 

12  111). 

-L'riiii-  (.March  27  28,    12  in.   to 

1,600 

.79 

12.  (i4 

.72 

11.52 

.  083 

133 

I    Viiu.i. 

54 


Table  26. — Nitrogen 

and  carbon 

in  urine  and  feces- 

—Continued. 

Lab- 
ora- 
tory 
num- 
ber. 

Urine  and  feces. 

0 
o 

1 

Nitrogen. 

Carbon. 

Fuel 

value 

per 

gram. 

Total 
fuel 
value. 

Kemarks. 

5024 

5025 
502(J 

rUrine  (March  28-29,   12  ni.  to 
12  m.). 

Urine  (March  29-30,   12  m.  to 
12  ni.). 

Urine  (March  30-31,   12  m.  to 

,    12  m.). 

fUrine  (March  31-April  1,  12  m. 

1     to  12  ra.). 

lUrine(April  1-2, 12m.  tol2m.K. 

[Urine  (April 2-3, 12m.  to  12m.) . . 

rUrine  (April 3-4, 12ni.  to  12  m.) . . 
1  Urine  (April  4, 12  m.  to  9  p.  m.) . . 

Total 

Oms. 
1,713 

L107 

1,422 

662 

841 

798 

1,529 
822 

Per 
cent. 
0.70 

1.12 

.92 

L77 

1.95 
L79 

L05 
.65 

0ms. 
11.90 

12. 40 

13.08 

11.68 

16.40 
14.29 

16.13 
5.34 

Per 

cent. 
0.76 

.76 

.76 

1.31 

1.31 
L31 

.73 
.73 

Gms. 
13.  02 

8.41 

10.81 

8.67 

11.02 
10.45 

11.16 
6.00 

Cal- 
ories. 
0.089 

.089 

.089 

.151 

.151 

.151 

.055 
.055 

Cal- 
ories. 
152 

99 

126 

100 

127 
121 

84 
45 

.No  work. 

1  Muscular 
(    work. 

(S  upplemen- 
<     tary    ]ieriod, 
[    no  work. 

13,  907 

25.4 

304. 8 

5.46 

163. 90 

L39 

16.64 

4i."40' 

119. 33 
10.52 
126. 20 

4.723' 

1,311 

120 

1,440 

2761 

Pece.s  (average  for  1  day ) 

Total 

The  amount  of  carbon  dioxid  produced  during-  the  period  in  the 
respiration  chamber  is  shown  in  Table  27. 

Table  27. — Carbon  dioxid  produced  in  respiration  experiment  No.  4. 


Date. 


Period. 


Ventila- 
tion 
(volume 
of  air). 


COj  per  liter. 


In  incom- 
ing air. 


In  outgo- 
ing air. 


Given 

off  by 

subject. 


Total 
weight 
COj  ex- 
haled by 
subject. 


Total 

weight  C 

exhaled 

in  CO2. 


March  23,  3  p.  m.,  to 
March  24,  6  a.  m 


to  I 


March  24,  6  a.  m.,  to 
March  25,  6  a.  m. 


March  25,  6  a.  m.,  to 
March  26,  6  a.  m. 


March  26,  6  a.  m.,  to 
March  27,  0  a.  m. 


March  27,  6  a.  m.,  to 
March  28,  6  a.  m. 


March  28,  6  a.  m.,  to 
March  29,  6  a.  m. 


March  29,  6  a.  m.,  to 
March  30,  6  a.  m. 


March  30,  6  a.  in.,  to 
March  31,  6  a.  m. 


March  31,  6  a.  m..  to 
April  1,  6  a.  m. 


3  p.m.  to 9 p.m. 
9  p.  m.  to  3  a.  m. 

3  a.m.  to  9  a.m. 


9  a.m. 
3  p.m. 
9  p.m. 

3  a.m.  to 9  a.m. 


.  to  3  p.m. 
.to  9  p.  m. 
.to 3  a.m. 


•  to  3  p.m. 
.to 9  p.m. 
.to  3  a.  m. 


9  a.  m 
3  p.  m 
9p.  m 

3  a.m.  to  9  a. m 


9  a.m. 
3  p.  m. 
9  p.  m. 

3  a.m. 

9  a.m. 
3  p.m. 
9  p. 

3  a.m.  to  9  a.m... 


to  3  p.m. 
to  9  p.  m . 
to  3  a.  ni- 


.  to  3  p.m. 
.  to  9  p.  m . 
.  to 3  a.m. 


.to  3  p.m. 
.to  9  p.m. 
.  to  3  a.  m . 


9  a.  m.  1 
3  p.  m. 
9  p.m. 

3  a.  m.  to  9  a.  m. 


9  a.m. 
3  p.m. 
9  p.m. 

3  a.m. 

9  a.m. 
3  p.  m. 
9  p.m. 

3  a.  lu. 

9  a.m. 
3  p.m. 
9  p.m. 

3  a.m. 


to  3  p.m. 
to9  p.  m. 
to 3  a.m. 


to  3  p.  m. 
to 9  p.m. 
to 3  a.m. 


to  3  p.  m . 
to  9  p.  m. 
to  3  a.  m . 


Liters. 

21,  840 
23,  348 

23,  606 

20,  962 
21,420 

22,  288 

21,370 

21,  .350 
21,970 
21,060 

21,  370 

21,  240 
22,110 

20,  760 

21,  470 

20,  760 
21,780 
22, 190 

21,010 

20,  600 
21,220 

21,  520 

20,  350 

20,  050 

21,  290 
20,  790 

20,  350 

21,  320 
21,  290 
21,  976 

20,  354 

21,  040 
21,240 
20,  750 

20,  240 


Mg. 
0.62 
.59 


.58 
.59 
.57 


.56 
.59 
.56 


.56 
.57 
.55 


.58 
.60 
.57 


.63 
.59 
.55 

.56 

.58 
.60 
.61 


.58 
.61 
.58 


Mg. 
10.48 
9.42 


12.76 
11.89 
9.05 


12.77 
11.96 
10.34 

8.71 

12.28 

11.44 

9.47 


10.96 

11.05 

9.05 

9.01 

11.32 
12.52 
11.31 


12.30 
11.60 
9.51 


12.20 
10.72 
10.88 


21.09 
20.37 
11.20 


Mg. 
9.86 
8.83 


12.18 
11.30 
8.48 

8.73 

12.22 
11.  36 
9.72 


11.72 
10.85 
8.91 


10.40 
10.48 
8.50 

8.45 

10.74 
11.92 
10.74 

8.64 

n.67 

11.01 

8.96 


11.62 
10.12 
10.27 

10.90 

20.51 
19.76 
10.62 

9.22 


Orams. 
214.9 
206.3 
189.3 
189.3 
255.2 
242.2 
189.1 
193.2 
193.3 
260.8 
249.6 
204.8 
'87.3 
187.3 
248.9 
239.9 
184.9 
188.2 
'88.1 
215.8 
228.2 
188.7 


221.4 
252.9 
23L2 
187.9 
188.0 
240.9 
234.5 
186.2 
19L7 
19L7 
247.8 
215.5 
225.8 
1 110. 9 
1 110.  9 
431.6 
419.6 
220.6 
'93.3 
'93.4 


rams. 
139.  2 


237.0 


244.3 


220.7 


240.6 


243.2 


348.0 


'Each  experimental  day  ended  at  6  a.  m. ;  therefore  the  amount  of  CO-^  in  the  period  from  3  a.  m.  to 
9  a.  m.  is  divided  equally  between  the  two  days. 


55 

Tablk  27. — Carbon  diuxid jfioduced  in  resjy'iration  experiment  No.  4 — Continued. 


Date. 


Period. 


i    9 
April  1.   6  a.  ni.,  to     ,  ., 

April  "J,  6  .a.  iii 


a.  m 
p.  m 
p.  lU 


to  3 
to  9 
to  3 


p.m. 
p.  ni. 
ii.  111. 


April  2.  6  a.  m.,  to 
April  3,  6  a.  m. 


.\pril  3.    6  a.  in.,  to 
Ajdil  4.  0  a.  III. 

April   4,  6  a.  ni.,  to  ( 
April  4,  3  i>.  lu.       \ 


9] 

3  a.  III.  to!),  a.  in. 

9: 

3] 

9] 

3  a. ui.  to 9  a.m.. 


I  a.  III. 
I  p.  Ill, 
I  p.  Ill, 


t..3 
to  9 
to  3 


11.111. 
a.  III. 


a.  m. 
p.  m, 
]i.  Ill 


to  3 
to  9 
to3 


3  a.m.  to  9 
9  a.  m.  to  3 


p.  Ill . 
p.  111. 
a.  111. 

a.  III. 

p.  111. 


Ventila- 
tion 
(volume 
of  air). 


CO2  per  liter. 


lAtert. 
21.  290 
21,330 
20, 890 

19,  390 

19,  972 
21.400 
21,941 

20,  820 

20,  fi86 
21.360 
21, 125 

20,  57:) 

21,268 


In  incom- 
ing air. 


(1.65 
.63 
.62 

.71 

.61 
.65 

.83 

1.55 

.83 

.87 
1.23 

1.94 

.57 


In  outgo- 
ing air. 


Given 

oft"  by 

subject. 


Mg. 
24. 18 
22.  73 
11.36 

10.94 

23.92 
24.62 
11.  39 


11.86 
13.40 
11.29 

10.86 

12.44 


Mg. 
23.53 
22. 10 
10.74 

10.23 

23.  31 
23.  97 
10.  56 

8.72 

11.03 
12.53 
10.06 

8.92 

11.87 


Total 
weight 
COj  ex- 
haled by 
subject. 


Total 
weight  C 
exhaled 
in  CO.,. 


Grains. 
500.9 
471.4 
246.0 
'  99. 1 
'  99.  2 
465.6 
512.9 
231.6 
■90.8 
190.8  \\ 
228.2  ' 
266.  S    \ 
212.4 
'91.8    J 
'91.8    \ 
252.5    / 


(Ira  ins. 


'  Each  experimental  day  eniled  at  6  a.m.;  therefore  the  amount  of  CO^  in  the  period  from  3  a.  ni.  to 
9  a.  m.  in  divided  eijuall.y  between  the  two  days. 

The  balance  of  income  and  outgo  of  nitrogen  and  carbon  made  up 
from  data  given  in  Tables  25,  20,  and  27  is  shown  in  the  following 
table  : 

T.vuLK  28. — Ualancc  of  income  and  outijo  of  nitrogen  and  carbon  (renpiralion  experiment 

'  No.  4). 


Date. 


March  23-24,   9 

p.  III.  to  12  III... 
March  24-25,  12 

III.  to  12ui 

ilaich  2.5-26,  12 

III.  to  12  m 

March  26-27,  12 

ui.  to  12  m.... 
Man  b  27-28,  12 

ni.  tci  12 m 

March  28-29,  12 

m.  to  12m 

March  29-30,  12 

ni.  to  12m 

ilarch  30-31,  12 

m.  to  12  m 

March  31-April 

1. 12  III.  to  12  m 
April  1-2,  12  m. 

to  12  m 

April  2-3,  12m. 

to  1 2  m 

April  3-4,  12m. 

to  12  III 

A  pril  4. 12  m.  to 

9  p. lu 


Nitrogen. 


In 
food. 


0  ms. 
10.1 

16.2 

16.2 

16.2 

16.2 

16.2 

16.2 

16.2 

16.2 

16.2 

16.2 

16.2 

6.1 


In        In 
uriue.i  feces- 


Total,12(lay8l94.4 


Gmn. 
9.1 

14.1 

13.1 

13.7 

12.6 

11.9 

12.4 

13.1 

11.7 

16.4 

14.3 

16.1 

5.4 


Gms.  Gms. 

0.9  I  -f  0.1 

I     1.4  !  -fO.7 

1.4  '  -fl.7 

I     1.4  -hl.l 

I     1.4-1-2.2 

'     1.4  -1-2.9 

1.4  +2.4 

1.4  +1.7 

1.4  I  +3.1 

1.4  —1.6 

1.4  I  +0.5 

1.4  —1.3 

.5  1^0.2 


Carbon. 


In      I     In 
food,    iuriue. 


103.9 


Gramg. 
152.  6 

244.1 

244.1 

244.1 

244.1 

244.1 

244.1 

244.1 

244.1 

244.1 

244.1 

244.1 

91.5 


16.8   +13.7  ,2,929.2 


Gms. 
5.9 

7.6 

5.9 

8.9 

11.5 

13.0 

8.4 

10.8 

8.7 

11.0 

10.4 

11.2 

6.0 


119.3 


In  res- 

In 
feces. 

pira- 
tory 
prod- 
ucts. 

Gms. 
6.6 

Grams. 
139.  2 

10  5 

237.0 

10.5 

244.3 

10.5 

231.6 

10.5 

220. 7 

10.5 

240.6 

10.5 

229.4 

10.5 

243.2 

10.5 

348.0 

10.5 

384.8 

10.5 

381.8 

10.5 

242.7 

3.9 

93.9 

120.0 

3, Zil.  2 

Gain 

(  +  )or 
loss 

(-)■ 


Grams. 

+     0.9 

—  11.0 

—  16.6 

—  6.9 
+    1.4 

—  20.0 
4.2 

—  20.4 
123.1 

—162. 2 
—158. 6 

—  20.3 

—  12.3 


Fuel  value. 


-553.3 


Of 
food. 

Of 
urine. 

Calo- 
ries. 
1, 713 

Calo- 
ries. 
67 

2,741 

87 

2,741 

68 

2,741 

102 

2,741 

133 

2,741 

152 

2,741 

99 

2,741 

126 

2,741 

100 

2,741 

127 

2,741 

121 

2,741 

84 

1,028 

45 

32, 892 

1,311  1 

Of 
feces. 


Calo- 

riei. 

75 

120 

120 

120 

120 

120 

120 

120 

120 

120 

120 

120 

45 


1,440 


56 

The  calculated  gains  and  losses  of  protein  and  fat  are  shown  in  the 
following  table : 

Table  29. — Gain  or  loss  of  protein  and  fat  {respiration  experiment  No.  4). 


Date. 

Nitrogen 
gained 

(+)or 
lost  (— ). 

Protein 
gained 
(  +  )  or 

lost  (— ). 

Total 
carbon 
gained 
(  +  )  or 
lost  (— ). 

Carbon  in 

protein 

gained 

(  +  )  or 

lost  (— ). 

Algebraic  dif- 
ference be- 
tween total 

carbon 

and  carbon 

in  protein 

(=M). 

Fat 
gained 
(+)or 
lost  (— ) 
(M-j- 
0.765). 

March  23-24,9  p.  m.  to  12  m 

Or  anas. 
■+0.1 
+0.7 
+  1.7 
+  1.1 
+2.2 
+  2.9 
+  2.4 
+  1.7 
+  3.1 
—1.6 
+  0.5 
—1.3 
+0.2 

Grams. 
+  0.6 

+  4.4 
+  10.6 
+  6.9 
+13.8 
+  18.1 
+15.0 
+  10.6 
+  19.4 
—10.0 
+  3.1 
—  8.1 
+  1.2 

Grams. 
+     0.9 

—  11.0 

—  16.6 

—  6.9 
+     1.4 

—  20.0 

—  4.2 

—  20.4 

—  123.1 
—162.  2 
—158.  6 

—  20.3 

—  12.3 

Grams. 
+  0.3 
+  2.3 
-1-  5.6 
+  3.7 
+  7.3 
+  9.6 
+  8.i 
+  5.6 
+10.3 

—  5.3 
+  1.6 

—  4.3 
+  0.6 

Grams. 
+    0.6 

—  13.3 

—  22.2 

—  10.  6 

—  5.9 

—  29.6 

—  12.2 

—  26.0 
—133.  4 
—156.  9 
—160.  2 

—  ICO 

—  12.9 

Grams. 
+     0.8 
17  4 

March  24  25  12  ni  to  12  lu       

March  25  26  12  m.  to  12  m  

29  0 

March  26  27  12  m.  to  12  m 

13  8 

March  27  28  12  m.  to  12  m 

7  7 

Marcli  28  29  12  m.  to  12  m  

38  7 

March  29-30, 12  m.  to  12  ra 

March  30  31  12  m.  to  12  m 

—  15.9 
34  9 

March  31-April  1,  12  m.  to  12  m 

April  1  2, 12  m.  to  12  m 

—174.4 
205  1 

April  2  3, 12  m.  to  12  m 

209  4 

April  3-4, 12  m.  to  12  m 

20.  9 

April  4, 12  m.  to  9  p.  m 

16.9 

Total,  12  days 

+13.7 

+  85.6 

—553. 3 

+45.3 

—598.  6             789  4 

DISCUSSION   OF   RESULTS. 


VENTILATION  AND   PRODUCTION   OF   CARBON  DIOXID. 

The  observations  regarding  ventilation  and  the  eifects  of  the  presence 
of  carbonic  acid  in  large  quantities  are  of  decided  interest.  The  incom- 
ing air,  which  was  ordinary  fresh  air  from  the  outside  of  the  building, 
contained  on  the  average  from  0.5  to  0.6  of  a  milligram  of  carbon 
dioxid  per  liter;  in  the  outgoing  air  the  amount  of  carbon  dioxid  aver- 
aged about  11  milligrams  per  liter,  though  the  variations  from  this 
amount  were  considerable.  In  the  last  experiment,  especially,  the  dif- 
ferences in  bodily  activity  in  the  different  i:»eriods  were  very  large,  and 
the  differences  in  carbon  dioxid  exhalation  were  correspondingly  great. 
The  results  are  epitomized  in  Table  30,  which  shows  the  quantities  of 
air  supplied  and  carbon  dioxid  jDroduced  in  each  of  the  four  experi- 
ments : 

Table  30. — Amount  of  carbon  dioxid  produced  in  the  respiration  apparatus. 


Experi- 
ment 
num- 
ber. 

Subject. 

Occupation. 

Dura- 
tion of 
experi- 
ment. 

Air 
sup- 
plied 
per 
miuute. 

Amounts  of  CO2  per  liter 
in  outgoing  air. 

Average 
amount 
of  CO, 
given  off 
in  24 
hours. 

Mini- 
mum. 

Maxi- 
mum. 

Aver- 
age. 

1 

Janitor  (E.  0.) 

do 

Eest 

Days. 

2i 

2i 
5 

1| 
3 
3 
3 

IJ 

Liters. 
49 
50 

75 

55 
55 
55 
55 
55 

Mg. 
8.0 
8.1 
4.6 

8.1 

8.7 
9.0 
9.9 
10.9 

Mg. 
13.4 
12.7 
9.9 

12.8 
12.8 
12.5 
24.6 
13.4 

M<i. 
11.0 
10.4 

7.4 

10.2 
10.5 
10.9 
16.9 
11.8 

Grams. 
778  B 

2 

...    do         

794  6 

3 
4 

Chemist  (O.E.T.) 

Physicist  (A.W.  S.)  .. 
Average,  12  days 

Light  mental 
work. 

(•Pest 

Mental  work 

Rest 

Muscular  work  . 
Kest 

806. 4 

848.9 

851.5 

871.7 

1,362.3 

897.7 

12                .^.'i   1          8-  1 

24.6 

12.1 

989.2 

57 

The  table  sliows  that  the  quantity  of  carbou  dioxid  in  the  incoming 
air  was  normal,  ranging  from  0.55  to  ().6()  milligrams  per  liter.  The 
ventilation  in  experiments  Nos.  1  and  2  was  at  the  rate  of  about  50 
liters  of  air  per  minute;  the  carbon  dioxid  in  the  outgoing  air  varied 
from  8  to  13.4  and  averaged  10.7  milligrams  per  liter. 

In  experiment  No.  3,  Avith  an  average  ventilation  of  75  liters  of  air 
per  minute,  the  range  of  carbon  dioxid  in  the  air  was  from  4.G  to  9.0 
milligrams  per  liter  and  the  average  7.4  milligrams  per  liter.  The 
smaller  qiumtity  of  carbon  dioxid  in  the  air  as  compared  with  experi- 
ments !Nos.  1  and  2  was  due  to  the  larger  ventilation,  since  the  average 
weight  of  carbon  dioxid  given  off  in  twenty-four  hours  was  84.S.9  grams 
as  compared  with  778.0  grams  in  experiment  No.  1  and  794.0  in  experi- 
ment No.  2.  In  these  experiments  the  subject  was  either  at  rest  or 
engaged  in  light  mental  work  or  reading. 

Experiment  No.  4  is  of  much  more  interest  in  this  connection,  since 
the  differences  in  mental  and  physical  exercise  were  much  wider. 
During  the  lirst  and  fifth  periods  of  one  and  five-eighths  and  one  and 
three-eighths  days,  res[)ectively,  the  subject  was  at  rest.  During  the 
second  period,  which  lasted  three  days,  he  was  engaged  in  rather  severe 
mental  work.  The  third  period  was  one  of  as  nearly  absolute  rest  as  was 
l)racticable.  In  the  fourth  i)eriod  the  subject  was  engaged  in  severe 
muscular  work  for  eight  hours  per  day.  The  rate  of  ventilation  was 
55  liters  i^er  minute.  The  temperature  of  the  air  in  the  chamber  was 
generally  from  19°  to  20^'  C,  though  it  fell  at  times  to  17°  and  rose 
during  the  periods  of  hard  muscular  work  to  22°. 

The  weight  of  carbon  dioxid  given  oft'  in  twenty- four  hours  ranged 
from  about  850  to  900  grams  for  the  days  at  rest  and  was  no  larger  with 
mental  work,  but  averaged  over  1,300  grams  for  the  days  of  muscular 
work.  During  two  periods  of  six  hours  each  of  hard  muscular  work 
the  elimination  of  carbon  dioxid  reached  513  and  501  grams,  respec- 
tively. During  the  night,  or  sleeping  period,  the  exhalation  of  carbou 
dioxid  was  singularly  constant  irrespective  of  the  day's  occupation.  It 
amounted  to  175  grams  in  six  hours,  with  but  slight  variation  from  that 
figure.' 

The  weight  of  carbon  dioxid  in  the  outgoing  air  during  the  periods 
of  rest  and  mental  work  ranged  from  8.1  to  13.4  milligrams  per  liter, 
but  aveiaged  not  far  from  11  milligrams  per  liter.  During  the  i)eriod 
of  muscular  work,  however,  the  range  was  from  9.9  milligranis  per  liter 
in  the  hours  of  rest,  e.  g.,  at  night,  to  24.0  milligrams  per  liter  in  the 
hours  of  severe  work. 

Authorities  on  ventilation  commonly  estimate  the  maximum  of  carbon 
dioxid  pcr(nis.sil)lein  the  air  of  inhabited  rooms  atone  part  i)ei'  thousan*! 
by  volume,  which  corresjtonds  to  about  1.97  milligrams  of  carbon  dioxid 

'Fr»r  rcc«iit  obscrviitioiis  of  thn  vnriatioiiB    hi   tlio   amount  of  (^arhon   dioxid 

(-,\(vvU*\  duriiifj  H]it'-]}\ufi  and  vvakiiifj  and  under  varionH  coiiilitioiiH  of  work  and 
rcHt,  Hci-  invcHti^jatiiinH  liy  Sond<^ii  and  Tif^iTHlfdl  ('Skainl.  Arrli.  I'liyniol.,  <!  (l«l)r»), 
NoM.  l-;j,  pp.  1-221;  al)tttia(;t<d  in  i;xp<  rinuiit  Station  Iv'nconl  H,  p.  L'lL'j. 


58 


per  liter.  It  will  be  observed  that  the  amounts  of  carbon  dioxid  in  the 
air  itt  the  respiration  chamber  during  these  experiments  was  from  8  to 
25  milligrams  per  liter,  and  averaged  10  to  12  milligrams  per  liter.  In 
other  words,  the  subjects  of  these  experiments  lived  constantly  in  an 
atmosphere  containing  from  five  to  six  times  the  amount  of  carbon  dioxid 
in  the  standard  just  referred  to.  In  experiment  No.  1  the  carbon  dioxid 
rose  to  nearly  tliirteen  times  the  amount  in  the  standard. 

The  interesting  fact  in  this  connection  is  that  no  one  of  the  sub- 
jects appeared  to  experience  any  inconvenience  whatever  from  either 
these  large  amounts  of  carbon  dioxid  or  from  any  other  products  of 
exhalation. 

The  subject  who  remained  in  the  apparatus  during  the  five  days  of 
the  third  experiment  was  as  comfortable  in  every  way,  according  to  his 
repeated  statements  both  during  the  experiment  and  afterwards,  as  if 
he  had  been  in  a  room  supi^lied  with  a  larger  amount  of  air.  Even 
in  the  fourth  experiment  the  subject  was  not  aware  of  the  least  incon- 
venience or  discomfort  during  the  twelve  days  of  his  sojourn  in  the 
chamber. 

It  maybe  added  that  these  results  are  in  accord  with  the  late  experi- 
ments by  Billings,  Mitchell,  and  Bergey,^  which  imply  that  the  discom- 
fort experienced  in  poorly  ventilated  rooms  is  not  due  to  the  excess 
of  carbon  dioxid.  It  seems  probable,  however,  that  one  cause  of  the 
discomfort  felt  in  badly  ventilated  rooms  occupied  by  a  number  of  people 
may  be  the  large  amount  of  moisture  which  accumulates  in  the  air,  while 
at  the  same  time  the  temperature  rises.  Some  of  the  observations 
made  in  the  experiments  above  described  accord  with  this  hypothesis.^ 

In  anticipation  of  a  special  treatment  of  this  phase  of  the  experiments 
in  another  place,  further  discussion  is  omitted  here. 

NUTRIENTS  AND  FUEL  VALUES. 

The  nutrients  and  fuel  values  of  the  food  eaten  and  digested  in  the 
four  experiments  are  briefly  summarized  in  the  following  table: 

Table  31. — Total  and  digested  nutrients  and  fuel  value  of  daily  food  in  the  four  respiration 

experiments. 


Exper- 
iment 
num- 
ber. 

Subject. 

Dura- 

In total  food. 

In  digested  food. 

tion 
of  ex- 
peri- 
ment. 

Pro- 
tein. 

Fat. 

Carbo- 
hy- 
drates. 

Fuel 
value, 
deter- 
mined. 

Pro- 
tein. 

Fat. 

Carbo- 
hy- 
drates. 

Fuel 

value, 

deter- 

mined.a 

1 
2 
3 

4 

Janitor  (E.  0.) 

..-.do 

Chemi8t(0.F.  T.).. 
Physicist  (A.W.  S.) 

Days. 

I' 

12 

Grams. 
142 
120 
96 
101 

Grams. 
126 
112 
73 
85 

Grams. 
296 
281 
338 
329 

Cal- 
ories. 
3,230 
2,925 
2,645 
2,740 

Grams. 

136 

110 

90 

93 

Grams. 

123 

109 

69 

62 

Grams. 

290 
277 
331 
321 

Cal- 
ories. 
2,  970 
2,650 
2,460 
2,510 

a  Fuel  value  of  total  food  less  that  of  feces  and  urine. 


'  On  the  composition  of  expired  air  and  its  eifect  on  animal  life.  Smithsonian  Con- 
tributions to  Knowledge,  Vol.  XXIX  (No.  989,  Hodgkius  fund). 

2Defren  (Tech.  Quart.,  9  (1896),  No.  2-3,  p.  238;  E.  S.  E.,  8,  p.  385)  has  suggested 
that  the  deleterious  effect  of  badly  ventilated  rooms  may  be  due  to  the  presence  of 
nitrites,  which  he  has  found  In  considerable  quantities  in  the  air  of  such  rooms. 


59 


The  balance  of  income  and  outgo  of  nitrogen  and  carbon  and  the  gain 
or  loss  of  body  protein  and  fat  in  the  four  experiments  are  briefly  sum- 
marized as  follows : 

Tablk  32. — Balance  of  income  and  outgo  of  nitrogen  and  carbon  and  gain  or  Ions  of  body 
protein  and  fat  in  the  four  riS2)iration  experiments. 


a. 

Nitrogen. 

Carbon. 

Pro- 
tein. 

Fat. 

§1 

<u 

bi 

>i 

^ 

^^ 

t4 

Subject. 

Occupa- 
tion. 

o  a 

o 
— ■  1 

3  . 

o 

o 

O 

1" 

ja 

•d 

6 
a 

a> 

+  J, 

_■ 

6 
a 

i 

f-  a 
»5 

+x 

+  1 

+  J, 

1^ 

1 

1 

a 

M 

.9  = 
o 

S 

a 
t-1 

i 

a 

M 

.s  = 
o 

.9  = 

a'~' 

.si 

a" 
O 

Days. 

Gm«. 

Oms. 

Oi. 

Got*. 

Gw*. 

(hnx. 

Gmg. 

6ms. 

Gins. 

Otns. 

Oms. 

1 

Janitor 
(E.O.). 

Rest .... 

2 

45.4 

39.2 

1.8 

+  4.4 

578.6 

22.7 

18.0 

428.2 

-1-109.7 

+27.5 

+124. 3 

2 

....do 

....do... 

2 

3«.4 

30.1 

3. 2  —  0. 9 

521.2'  28.6 

19.  S 

435. 1 

+  37.7 

—  5.7 

+  .'>3.2 

3 

Cliemist 

Light 

5 

70.5 

68.7 

4.  5  +  3.  3 

1,171.5   54.6 

34.  51, 099. 6 

—  17.2 

+20.6 

—  36.7 

(O.F.T.). 

mental 
work. 

Rest.... 

H 

2G.3 

23.2 

2.3+  0.8 

396.7 

13.5 

17.1 

376.2 

—  10.1 

-t    5.0 

—  16.6 

il  e  ntal 

3 

48.6 

39.4 

4.2+  5.0 

732. 3 

26.3 

31.5 

690.6 

—  22.1 

+  31.3 

-  50.5 

work. 

4 

Physicist 
(A'W.S.). 

Rest .... 

3 

48.6 

37.4 

4.21+  7.0 

732.3 

32.2 

31.5 

713.2 

—  44.6 

+43.  7 

—  88.6 

Mil  sca- 
lar w'k. 

3 

48.6 

42.4 

4.2 

+  2.0 

732.3 

30.1 

31.51,114.6 

-443.9 

+  12.5 

-588. 9 

Rest .... 

11 

22.3 

21.5 

1.9 

-  1.1 

335.  6 

17.2 

14.4     336.6 

—  32.6 

-6.9 

—  37.8 

Whole 

12 

194.4 

163.9 

16.8 

-t-13. 7  2, 929.  2119. 3|126. 0|3, 237. 2 

-555. 3 

+85.6 

-782.4 

exp't. 

1           1           1 

As  explained  previously,  the  total  income  is  represented  by  the  food 
actually  eaten  (with  drink  and  tlie  oxj^gen  of  inhaled  air),  and  the  net 
income  by  the  total  income  minus  the  outgo  in  the  feces,  taking  into 
account  also  the  incompletely  oxidized  material  excreted  in  the  urine. 
The  net  income  represents  that  part  of*  the  food  which  is  available  for 
the  body.  If  the  amount  available  is  Just  sufficient  for  the  needs  of 
the  organism  it  will  all  be  burned  in  the  body  to  yield  energy.  If  it  is 
insufficient  some  of  the  body  tissue  will  be  burned  also,  and  if  it  is  more 
than  sufficient  some  material  may  be  stored.  The  nitrogen  in  the  urine  is 
assumed  to  represent  the  nitrogenous  material  which  has  been  (incom- 
pletely) burned  in  the  body.  In  the  present  experiments  it  is  assumed 
that  the  carbon  in  the  urine  is  from  the  same  source.  The  carbon  of 
the  respiratory  products  is  taken  as  representing  the  carbon  which  has 
been  comidetely  burned. 

In  Table  33  are  shown  the  nitrogen,  carbon,  and  energy  in  the  daily 
n(!t  income  and  the  material  actually  burned  in  the  body  in  the  four 
experiments. 


60 


Table  33. — Daily  net  income  and  material  actually  im-ned  in  the  dody  in  the  four 

experiments. 


Ex- 
peri- 
ment 
num- 
ber. 

Subject. 

Occupation . 

Dura- 
tion 

of  ex- 
peri 

ment. 

Digested  food. 

Material  burned  in  the 
body. 

Nitro- 
gen. 

Carbon. 

Pnel 
value. 

Nitro- 
gen, a 

Carbon . 
6 

Fuel 
value. 

1 

Janitor  (E.  0.).-.. 
do         

Kest 

Days. 
2 
2 
5 

If 
.3 
3 
3 

Grams. 
21.8 
17.6 
14.4 

14.8 
14.8 
14.8 
14.8 
14.8 
14.8 

Grams. 
280.  3 
250.7 
227.  4 

233.6 
233.  0 
233.6 
233.6 
233.  C 
233.6 

Calories. 
2,  970 
2,650 
2,460 

2,525 
2,520 
2,495 
2,505 
2,  540 
2,510 

Gram,s. 
19.6 
18.0 
13.7 

14.3 
13.1 
12.5 
14.1 
15.2 
13.6 

Grams. 
225.5 
231.8 
230.9 

238.4 
241.0 
248.4 
381.6 
260.2 
279.7 

Calories. 
'  310 

2 

.   ...do 

2,420 
2,505 

2  585 

3 

Chemist  (O.F.T.). 

Physicist    (A.  W. 
S.). 

Light  mental 
work. 

fRest . 

4 

Mental  work . . 
Rest 

2,  620 
2  695 

Muscular  work 

4,325 
2,875 
3,085 

a  Nitrogen  of  urine,  i.  e.,  of  incompletely  oxidized  nitrogenous  material  of  food  and  body, 
b  Carbon  of  respiratory  products  plus  that  of  urine. 

Ill  the  first  experiment  the  amount  of  protein  was  rather  large.  The 
subject,  a  laboratory  janitor,  was  accustomed  to  somewhat  active  mus- 
cular work  and  had  a  very  hearty  appetite.  The  diet  was  of  his  own 
selection  and  proved  more  than  sufficient  for  the  needs  of  his  organism 
during  the  experiment  when  he  was  comparatively  inactive.  His 
organism  stored  both  protein  and  fat. 

In  the  next  experiment,  which  was  made  with  the  same  person,  the 
diet  was  the  same  in  kind,  but  less  in  quantity.  The  ration  proved 
insufficient  to  maintain  the  nitrogen  equilibrium,  although  some  fat 
was  stored.  In  this  case,  however,  the  quantities  of  protein  lost  and 
of  fat  gained  were  quite  small,  so  that  the  organism  was  very  nearly  in 
equilibrium,  especially  as  regards  nitrogen. 

In  the  third  experiment  the  diet  was  considerably  smaller  in  protein 
and  energy  than  in  the  two  preceding.  The  subject,  a  chemist,  was 
accustomed  to  rather  less  muscular  labor  than  the  subject  of  the  first 
and  second  experiments.  He  was  also  rather  lighter  in  weight.  The 
diet  which  he  chose  was  smaller  in  both  nutrients  and  energy.  The  fig- 
ures indicate  a  slight  gain  of  protein  and  loss  of  fat  during  the  exj)eri- 
ment,  but  on  the  whole  the  organism  Avas  very  nearly  in  equilibrium  in 
respect  to  both  nitrogen  and  carbon.  The  fuel  value  of  the  material 
actually  consumed  in  the  body  was  larger  than  in  either  of  the  two 
preceding  experiments,  though  somewhat  smaller  than  that  in  the  fourth 
experiment  under  similar  conditions. 

In  the  fourth  experiment  the  subject  was  a  physicist.  He  was  taller 
than  the  subject  of  the  third  and  heavier  than  either  of  the  subjects 
in  the  preceding  experiments.  The  diet  was  of  his  own  selection,  as 
in  the  previous  cases.  The  amount  of  nitrogen  was  less  than  in  the 
first  two  experiments,  though  slightly  more  than  in  the  third.  The 
potential  energy  of  the  digested  food  was  a  little  larger  than  in  that 
o±  the  third  experiment.     ^Nevertheless,  the  figures  indicate  a  slight 


6l~ 

gain  rather  tliaii  loss  of  protein  during  all  of  the  periods  of  the  e.xperi- 
meiit  wheu  there  Avas  uo  especially  great  luuscular  activity,  though 
there  was  constant  loss  of  fat  from  the  organism.  In  the  period  of 
muscular  activity  the  loss  of  fat  was  very  much  larger,  the  loss  of 
carbon  being  148  grams  per  day. 

In  discussing  the  gain  or  loss  of  protein  the  nitrogen  lag  is  an  imjior- 
tant  factor.  It  has  been  stated  above  that  in  experiment  No.  -4  au 
allowance  of  six  hours  was  made  for  the  lag  of  the  urine.  That  this 
time  was  iusufticient  was  also  pointed  out,  and  thirty  hours  Avas  sug- 
gested as  probably  more  nearly  representing  the  period  of  lag.  Table 
34  gives  the  nitrogen  and  carbon  in  the  net  income  and  outgo  for  the 
three  important  periods  of  this  experiment,  with  the  calculated  nitro- 
gen and  carbon  actually  burned  in  the  body  aud  energy  liberated, 
allowing  for  both  six  hours'  lag  aud  thirtj^  hours'  lag. 


Tahle  34. 


-Daily  net  invoine  and  material  actually  hurned  in   the  body,  allowing  for  6 
hours'  and  30  hours'  lag  of  urine. 


o 
e 

o 

t 
n 
o 

Nitrogen. 

Protein 
gain 
(  +  )or 

loss 

Carbon. 

Fat 
loss. 

In  di- 
gested 
food. 

In  ma- 
terial 
burned 
in  the 
body. 

Gain 

(+)  or 
loss 
(-)• 

Indi 
gestcd 
food. 

In  ma- 
terial 

burned 
in  the 
body. 

Loss. 

Fuel- 
value 
loss. 

Allowing  6  hours' 
lag: 

Menial  work 

Ke.st 

Days. 
3 
3 
3 

3 
3 
3 

Gramt. 
14.8 
14.8 
14.8 

14.8 
14.8 
14.8 

Grains. 
13.1 
12.5 
14.1 

12.7 
12.4 
15.6 

Grams. 
+1.7 
+  2.3 
+0.7 

+2.1 
+2.4 
—0.8 

Grams. 
+10.4 
+14.6 
+  14.2 

+  13.0 
+  15.0 
—  5.0 

Grams. 
233.6 
233. 6 
233.6 

233.  6 
233.  6 
233.6 

Grams. 
241.0 
248.4 
381.5 

243.3 
247.0 
382.4 

Grams. 

—  7.4 

—  14.8 
-147.  9 

—  9.7 

—  13.4 
-148.8 

Grams. 

—  16.8 

—  29.5 
—196. 3 

—  21.7 

—  27.8 
—191. 0 

Calories. 

—    100 

M 11  SCI  liar  work . 
A  UowingSO  hours' 
lag: 

Mental  work 

Kest 

—1, 820 

-    135 
180 

Muscular  work . 

—1, 825 

When  the  nitrogen  lag  is  assumed  to  be  six  hours  there  is  a  small 
gain  of  protein  <luring  the  period  of  muscular  work;  but  when  it  is 
assumed  to  be  thirty  hours  there  is  a  small  loss.  When  a  thirty-hour 
nitrogen  lag  is  assumed  the  gains  in  protein  during  the  periods  of  rest 
and  mental  labor  are  somewhat  larger  than  when  a  six-hour  lag  is 
assumed. 

It  will  be  noticed  that  there  are  marked  differences  in  the  ways  the 
sul)iects  in  the  four  exi)eriment8  utilized  the  food  material  at  tlieir 
ilisposal.  Tlie  dineiences  in  age,  weight,  occui>ation,  and  diet  have 
been  refcired  to.  It  will,  however,  be  of  interest  to  add  that  some 
studies  had  been  i)reviously  made  which  throw  a  little  more  light  upon 
the  <lietary  habits  of  two  of  them. 

Two  dietary  studies  were  made  in  the  family  of  the  laboratory  janitor, 
one  in  February  and  the  other  in  March,  18!M.'  In  these  tlie  average 
])rotein  in  the  food  eaten  per  man  per  day  was  estimated  at  120  grams, 

'  8eo  Report  of  Htorrs  (Couu.)  Agricultural  Experiuieut  Station,  18'J4,  pp.  IHO  :in<l  liiS. 


62 

and  the  total  energy  of  tlie  nutrients  at  3,900  calories.  The  correspond- 
ing amounts  digested  were  estimated  at  approximately  116  grams  of 
protein  and  3,660  calories.  This  was,  on  the  whole,  a  liberal  diet.  It 
is  slightly  larger  than  the  American  standard'  suggested  for  a  man  at 
moderately  severe  muscular  work. 

Two  dietary  studies  were  made  by  the  subject  of  experiment  No.  4 
at  his  home  in  a  country  town  in  another  State,  on  the  occasions  of 
vacation  visits,  one  in  the  winter  and  the  other  in  summer.^  There  was 
but  little  difference  between  the  results  of  the  two.  It  seems  fair  to 
assume  that  they  may  represent  the  dietary  habits  which  the  subject 
had  naturally  acquired.  The  averages  per  man  per  day  were  approxi- 
mately 79  grams  of  protein  and  3,125  calories  of  energy.  These  quan- 
tities are  estimated  to  correspond  to  about  71  grams  of  protein  and 
2,955  calories  of  energy  in  the  food  actually  digested. 

It  will  be  observed  that,  according  to  the  above  estimates,  the  labo- 
ratory janitor,  who  was  accustomed  to  moderately  active  muscular 
work  ten  hours  per  day,  and  who  was  what  would  be  called  a  "hearty 
eater,"  actually  burned  during  the  first  experiment  122  grams  of  the 
136  grams  of  digestible  protein  in  his  food  and  at  the  same  time  stored 
the  remaining  14  grams,  according  to  the  calculations  of  these  experi- 
ments. Of  the  2,970  calories  in  the  food  digested  he  burned  material 
.  corresponding  to  2,310  calories.  The  digested  nutrients  of  the  food 
furnished  an  excess  of  carbohydrates  and  fats  as  well  as  protein,  so 
that  his  organism  stored  fat  and  protein  corresponding  to  660  calories 
of  energy.  In  the  second  experiment  his  diet  was  reduced  so  as  to 
supply  only  110  grams  of  digestible  protein  and  2,650  calories  of  energy. 
In  this  case  his  organism  was  estimated  to  burn  113  grams  of  protein, 
a  trifle  more  than  the  food  supplied,  and  2,420  calories  of  energy.  The 
organism  gained  considerable  fat,  enough  to  make  a  gain  of  material 
corresponding  to  230  calories  of  energy. 

The  subjects  of  experiments  ISTos.  3  and  4,  who  were  accustomed  to 
only  light  muscular  activity,  chose  for  their  diet  materials  computed 
to  supply  90  and  93  grams  of  digestible  protein,  respectively,  and  other 
digestible  nutrients  sufficient  to  furnish  about  2,500  calories  of  energy 
per  day.  In  the  respiration  apparatus  when  at  rest  or  engaged  in 
either  light  or  severe  mental  work  they  burned  in  the  body  from  78  to 
86  grams  of  protein  and  from  about  2,500  to  2,700  calories  of  energy. 
It  was  evident  that  this  consumption  must  have  been  reasonably  eco- 
nomical, since  the  food  in  experiment  No.  3  supplied  only  a  trifle  more 
protein  and  a  trifle  less  energy  than  was  utilized;  while  in  experiment 
No.  4,  when  the  subject  was  at  rest  or  engaged  in  mental  work  there 
was  with  a  slight  apparent  gain  of  protein  a  decided  loss  of  fat.  Al- 
though the  subject  of  experiment  No.  4  was  a  man  of  larger  frame  and 
greater  weight  than  the  subject  of  experiment  No.  3,  his  organism 

lU.  S.  Dept.  Agr.,  Office  of  Experiment  Stations  Bui.  21,  p.  213. 
'^See  Eeports  of  Storrs  (Conn.)  Experiment  Station,  1895,  p.  137,  and  1896,  p.  144. 


63 

Imrued  less  protein  :  but  this  seems  to  accord  with  the  results  of  dietary 
studies  meutioued  above,  which  im[)lies  that  he  was  in  the  habit  of  con- 
suming small  quantities  of  protein.  While  his  organism  burned  smaller 
quantities  of  protein,  it  burned  more  fat  and  utilized  more  energj'  than 
was  the  case  with  the  subject  of  experiment  Jfo.  3.  When  the  same 
person  engaged  in  severe  muscular  work  the  amount  of  protein  burned 
rose  from  78  to  98  grams  per  day.  At  the  same  time  the  energy  utilized 
rose  from  2,695  to  4,.'525  calories.  That  there  should  be  such  an  increase 
in  the  amount  of  both  protein  burned  and  energy  utilized  with  the 
severe  muscular  work  is  not  at  all  suri)rising.  How  the  amount  of  pro- 
tein burned  during  the  period  of  muscular  work  would  have  been 
affected  if  the  quantity  of  carbohydrates  and  fats  had  been  sufficient 
to  sui)ply  the  needed  energy  is  a  question  to  be  answered  by  further 
experiment. 

OONCLrSIOJfS. 

The  experiments  above  described  offer  considerable  material  for  dis- 
cussion. Since,  however,  they  are  of  a  preliminary  character  and  are 
to  be  followed  by  others  in  which  the  results  of  the  experience  here 
obtained  will  be  used,  it  is  deemed  best  to  reserve  the  discussion  until 
more  of  the  anticipated  work  shall  have  been  accomplished.  Mean- 
while the  following  statements  are  i)erhai)S  in  place: 

(1;  The  experience  here  obtained  emjjhasizes  the  desirability  of 
longer  exi>erimeutal  j'criods  than  have  been  customary  in  experiments 
of  this  class.  Although  a  considerable  number  of  resjjiration  experi- 
ments have  been  made  with  animals  and  man,  the  periods  have  rarely 
exceeded  twentj'-four  hours.  The  hgures  in  the  tables  above  are  suffi- 
cient to  show  that  the  results  obtained  in  periods  so  short  are  less  con- 
clusive than  is  to  be  desired. 

(2)  Much  care  needs  to  be  bestowed  upon  the  analyses  of  the  mate- 
rials of  income  and  outgo.  In  tlie  majority  of  experiments  thus  far 
rejiorted  the  composition  of  food  and  solid  and  liquid  excretory  prod- 
ucts has  been  in  large  part  assumed,  ratljer  than  estimated  from  direct 
analyses  of  specimens  of  the  materials  belonging  to  the  experiments. 
In  like  manner  there  is  need  of  the  greatest  possible  care  and  accuracy 
in  the  determination  of  the  gaseous  excretory  products.  Xor  can  any 
of  the  organic  matters  given  oft'  in  ])ersi)iration  and  exhalation  be  left 
out  of  acc^>unt  if  the  fullest  accuracy  is  to  be  attained. 

(3)  It  is  to  be  hoped  that  future  exjierience  may  lead  to  sn(;h 
impiovements  as  shall  insure  the  accurate  measurement  of  all  the 
chemical  elements  involved  in  the  income  and  outgo.  It  is  evident  that 
there  are  no  insurmountable  obstacles  in  the  way  of  reasonably  accu- 
rate estimation  of  the  incom(;  and  outgo  of  nitrogen  and  carbon.  As 
regards  the  hydrogen,  the  difficulties  of  determination  ha\e  thus  far 
been  more  serious,  but  they  do  not  appear  to  be  by  any  means  insur- 
mountable. The  <juantitie8  of  sulphur  and  i)hosphoru.s  are  so  small 
that  extreme  accuracy  is  needed  for  their  estimation  in  order  to  insure 


64 

satisfactory  comparison  of  income  and  outgo.  The  experience  gained 
in  this  laboratory  since  the  exj)eriments  here  described  were  made  indi- 
cates that  by  refinement  of  methods  reasonably  reliable  results  may  be 
obtained. 

(4)  The  prospects  for  obtaining  a  satisfactory  balance  of  income  and 
outgo  of  energy  are,  on  the  whole,  decidedly  encouraging.  The  deter- 
minations of  heats  of  combustion  by  the  bomb  calorimeter  are  emi- 
nently satisfactory,  aud  there  seems  to  be  good  ground  to  hope  that 
ultimately  the  measurements  of  heat  given  off  from  the  body  may  also 
prove  sufficiently  accurate  for  such  purposes.  Satisfactory  results  have 
already  been  reported  by  other  experimenters  with  small  animals  and 
with  men  during  experiments  of  short  duration.  Experience  in  this 
laboratory  since  the  above  experiments  were  made  have  yielded  results 
agreeing  very  closely  indeed  with  the  theoretical  figures. 

(5)  The  results  of  these  experiments  and  of  similar  investigations 
elsewhere  bring  out  very  clearly  the  difference  in  the  amounts  of  nutri- 
ents and  energy  required  by  the  organisms  of  different  persons  under 
different  conditions,  and  confirm  the  results  of  previous  inquiry  in 
showing  that  muscular  labor  is  performed  at  the  expense  of  the  fats, 
sugars,  and  starches.  They  also  make  it  clear  that  the  body  may  draw 
upon  protein  for  this  j)urpose,  although  it  has  not  yet  been  determined 
just  what  are  the  conditions  under  which  this  is  done.  A  large  amount 
of  work  will  be  needed  to  secure  the  experimental  data  necessary  for 
accurate  generalizations.  The  importance  of  the  subject  is  such  as  to 
call  for  the  most  extensive  and  i^ainstaking  research. 


Date  Due 

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"D,;^a^.        Ml 

i-i%im' 

^Sile    ®    d 

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- 

.,  ;..     '-v^i^ 

^ 

COLUMBIA  UNIVERSITY  LIBRARlPg 


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^^,  Metabolism  of  Jiitrogea,^ 

and  carbo|n  in  the  human  organism 

.u^  1711941         P. 


